Tachometer apparatus and method for motor velocity measurement

ABSTRACT

A method and apparatus for determining the velocity of a rotating device is described herein. The apparatus includes a magnet assembly affixed to a rotating shaft of a rotating device and a circuit assembly. The circuit assembly includes a circuit interconnection having a sense coil and sensors affixed thereto. The circuit assembly is adapted to be in proximity to the magnet assembly, wherein the magnet assembly combines with the circuit assembly to form an air core electric machine such that voltages generated from the sense coil exhibits an amplitude proportional to the velocity

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisionalapplication No. 60/308,427, filed Jul. 27, 2001 the contents of whichare incorporated by reference herein in their entirety.

BACKGROUND

[0002] Speed sensors, or detectors of various types are well known inthe art. In recent years the application of speed detection to motorcontrol functions has stimulated demands on the sophistication of thosesensors. Rotational speed sensors are commonly configured in the samemanner as an electric machine, for example, a coil is placed inproximity to rotating magnets whereby the magnetic field induces avoltage on the passing coil in accordance with Faraday's Law. Therotating permanent magnets induce a voltage on the coil and ultimately avoltage whose frequency and magnitude are proportional to the rotationalspeed of the passing magnets.

[0003] Many of the tachometers that are currently available in the artexhibit a trade off between capabilities and cost. Those with sufficientresolution and accuracy are often very expensive and perhaps costprohibitive for mass production applications. Those that are inexpensiveenough to be considered for such applications are commonly inaccurate orprovide insufficient resolution or bandwidth for the application. Thus,there is a need, in the art for a low cost robust tachometer thatprovides sufficient accuracy and resolution for motor controlapplications and yet is inexpensive enough to be cost effective in massproduction.

SUMMARY

[0004] Disclosed herein is an apparatus for determining the velocity ofa rotating device comprising: a rotational part having a set of magnetassemblies affixed to a rotating shaft of the rotating device configuredto rotate about a rotation axis; and a circuit assembly including, acircuit interconnection having a sense coil, a sensor affixed to thecircuit assembly, mounted in close proximity to the rotating part, thecircuit assembly adapted to place components thereon in proximity to theset of magnet assemblies; wherein the set of magnet assemblies combinewith said circuit assembly to form an air core electric machine

[0005] Also disclosed herein is a system and method for determining avelocity of a rotating device, comprising the abovementioned apparatusand circuit assembly as well as a controller operatively coupled to thecircuit assembly. The controller is configured to execute an adaptivealgorithm including: receiving a position signal related to rotationalposition transmitted to the controller; determining a derived velocitysignal utilizing the position signal; receiving a tachometer velocitysignal; determining a compensated velocity signal in response to thetachometer velocity signal; and blending the compensated velocity signalwith the derived velocity signal under selective conditions to generatea blended velocity output indicative of the velocity of the rotatingdevice. The system is configured so that the compensated velocity signalis the resultant of an adaptive gain control loop configured to controlmagnitude of the velocity under selected conditions.

[0006] The system further includes another sense coil to form aplurality of sense coils, wherein the controller further receivesanother tachometer velocity signal to form a plurality of tachometervelocity signals.

[0007] A feature of the system is that the plurality of tachometervelocity signals is in quadrature.

[0008] Another feature of the system is that the plurality of tachometervelocity signals is substantially sinusoidal.

[0009] Also disclosed herein is a storage medium encoded with amachine-readable computer program code, the storage medium includinginstructions for causing a controller to implement a method fordetermining a velocity of a rotating device.

[0010] Yet another disclosure herein is a computer data signal embodiedin a carrier wave, the data signal comprising code configured to cause acontroller to implement a method for determining a velocity of arotating device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Referring now to the drawings wherein like elements are numberedalike in the several FIGURES:

[0012]FIG. 1 depicts the cross-section of the fixed and rotating partsof a tachometer;

[0013]FIG. 2 depicts a magnet assembly end-view illustrating thelow-resolution and high-resolution poles;

[0014]FIG. 3 depicts a partial view of a tachometer coil arrangement inthe circuit interconnection;

[0015]FIG. 4 depicts the expected output waveform from thelow-resolution sense coils;

[0016]FIG. 5 depicts a partial view of an alternative embodiment of thetachometer coil arrangement in the circuit interconnection board;

[0017]FIG. 6 depicts the expected output waveform from thehigh-resolution position sensor;

[0018]FIG. 7 depicts a top-level functional block diagram of a methodfor determination of the rotational speed;

[0019]FIG. 8A depicts the Speed Estimation process;

[0020]FIG. 8B provides a more detailed partial depiction of an exemplaryembodiment of the Speed Estimation process;

[0021]FIG. 9 depicts the Offset Compensation process;

[0022]FIG. 10 depicts the Get Phase process;

[0023]FIG. 11 depicts the Blend process;

[0024]FIG. 12 depicts the Align To Polled process; and

[0025]FIG. 13 depicts the Gain process.

[0026]FIG. 14 depicts a partial view of another alternative embodimentof the tachometer coil arrangement in the circuit interconnection boardfor sinusoidal output response;

[0027]FIG. 15 depicts a table and a vector diagram illustrating thevector contributions and combinations to the tachometer voltage;

[0028]FIG. 15A depicts the vector contributions to the fundamentalfrequency of the tachometer response;

[0029]FIG. 15B depicts the vector contribution and cancellation of thethird harmonic of the tachometer response;

[0030]FIG. 15C depicts the vector contribution and cancellation of thefifth harmonic of the tachometer response;

[0031]FIG. 15D depicts the vector contribution and cancellation of theseventh harmonic of the tachometer response;

[0032]FIG. 16 depicts two windings of one tachometer coil with rotationfor seventh harmonic cancellation;

[0033]FIG. 17 depicts four windings of two sense coils overlaid;

[0034]FIG. 18 depicts simplified view of two windings that comprise atachometer coil in an exemplary embodiment;

[0035]FIG. 19 depicts an alternative embodiment of a tachometer coil formagnetic field cancellation;

[0036]FIG. 20 depicts an exemplary cancellation coil for magnetic fieldcancellation;

[0037]FIG. 21 depicts a first tachometer coil, first winding of thecombined sinusoidal and interference cancellation configuration;

[0038]FIG. 22 depicts a first tachometer coil second winding of thecombined sinusoidal and interference cancellation configuration;

[0039]FIG. 23 depicts a second tachometer coil, first winding of thecombined sinusoidal and interference cancellation configuration;

[0040]FIG. 24 depicts a second tachometer coil second winding of thecombined sinusoidal and interference cancellation configuration;

[0041]FIG. 25 depicts a block diagram of the processing employed for thesinusoidal tachometer;

[0042]FIG. 26 depicts a speed estimation function;

[0043]FIG. 27 depicts an Offset Compensation process;

[0044]FIG. 28 depicts a Phase and Magnitude process;

[0045]FIG. 29 depicts a Velocity Blend Process; and

[0046]FIG. 30 depicts an auto-gain calculation function.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0047] Disclosed herein is a speed-sensing device hereinafter termed atachometer apparatus and methodology for determining the velocity of amotor as applied to a vehicle steering system. Such a tachometer may beutilized in various types of motors and other rotational devices suchas, for example, motors employed in a vehicle steering system. Apreferred embodiment, by way of illustration is described herein as itmay be applied to a motor tachometer in an electronic steering system.While a preferred embodiment is shown and described, it will beappreciated by those skilled in the art that the disclosure is notlimited to the motor speed and rotation in and electric power steeringsystem, but also to any device where rotational motion and velocity areto be detected.

[0048] Tachometers of various types are well known in the art. In recentyears the application of speed detection to motor control functions hasstimulated demands on the sophistication of those sensors. Many of thetachometers that are currently available in the art exhibit a trade offbetween capabilities and cost. Those with sufficient resolution andaccuracy are often very expensive and perhaps cost prohibitive for massproduction applications. Those that are inexpensive enough to beconsidered for such applications are commonly inaccurate or provideinsufficient resolution or bandwidth for the application. A tachometerwhich addresses both constraints is disclosed in copending commonlyassigned U.S. patent application Ser. No. 09/661,651 filed Sep. 14,2000. The referenced tachometer provides a structure and method by whicha velocity is determined. In that disclosure, an apparatus thatgenerates, and processes for computing, a velocity of a rotating device,therein an electric machine. Moreover, the apparatus disclosed thereingenerates and processes essentially trapezoidal velocity signals.Disclosed herein, are enhancements to that apparatus as well asadditional processes and embodiments, which generate and processessentially sinusoidal velocity signals.

[0049] Apparatus and Structure: Trapezoidal Response

[0050] Referring to FIG. 1, an existing tachometer structure 10comprising a rotational part 20 and a fixed part, a circuit assembly 30is depicted. The rotational part, 20 includes, but is not limited to, arotating shaft 22 and a magnet assembly 24. The rotating shaft 22 isconnected to, or an element of the device, (not shown) whose rotationalspeed is to be determined. Referring to FIG. 2, an axial (end) view ofthe magnet assembly 24 is depicted. The magnet assembly 24 is attachedto the rotating shaft 22 which rotates about a rotation axis 12 andincludes without limit, two concentric, annular magnets sets, a firstlow-resolution magnet set 26 of smaller radius surrounded by the secondhigh-resolution magnet set of larger radius. The concentric, annularconfigurations may be coplanar, but need not be. The low-resolutionmagnet set 26 comprises an inner annulus of the magnet assembly 24 isconstructed and configured as a six-pole alternating polarity permanentmagnet, with each pole comprising a 60 degree annular sector. Thehigh-resolution magnet set 28 comprises an outer annulus of the magnetassembly 24 is configured as a 72-pole alternating polarity permanentmagnet, with each pole comprising a 5 degree annular sector. While thepreferred embodiment utilizes the stated configuration, otherconfigurations are reasonable. The magnet structure need only beconfigured to allow adequate detection in light of the sensing elementsutilized, processing employed, and operational constraints. Thelow-resolution magnet set 26 and high-resolution magnet set 28 eachcomprise alternating north and south poles substantially equallydistributed around each respective annulus. One skilled in the art wouldappreciate that the magnets when rotated generate an alternatingmagnetic field, which when passed in proximity to a conductor (coil)will induce a voltage on the conductor. Further, using well-understoodprinciples the magnitude of the induced voltage is proportional to thevelocity of the passing magnetic field, the spacing and orientation ofthe coil from the magnets.

[0051]FIGS. 1 and 3 depict the circuit assembly 30. The circuit assembly30 includes, but is not limited to; a plurality of sense coils 40, alow-resolution Hall sensor set 34, and a high-resolution position sensor36. The circuit assembly 30 is placed parallel to and in close proximityto the axial end of the rotating magnet assembly 24. A circuitinterconnection 38 provides electrical interconnection of the circuitassembly 30 components and may be characterized by various technologiessuch as hand wiring, a printed card, flexible circuit, lead frame,ceramic substrate, or other circuit connection fabrication ormethodology. A preferred embodiment for the circuit assembly 30comprises the abovementioned elements affixed to a printed circuit boardcircuit interconnection 38 of multiple layers.

[0052] The sense coils 40 are located on the circuit assembly 30 in suchan orientation as to be concentric with the magnet assembly 24 about therotation axis 12 in close proximity to the inner annulus low-resolutionmagnet set 26. In a preferred embodiment, the sense coils 40 areconductive and an integral part of the circuit interconnection 38. Thesense coils 40 include, but are not limited to, two or more spiralingconductor coils concentrically wound in a serpentine fashion about therotation axis 12 such that each coil includes 24 turns comprising twotwelve turn windings on separate layers. Coil A is comprised of windings42 and 48 and coil B is comprised of windings 44 and 46. Each of thewindings is configured such that it spirals inward toward the rotationaxis 12 on one layer and outward from the rotation axis 12 on the secondlayer. Thereby, the effects of the windings' physical constructionvariances on the induced voltages are minimized. Further, the sensecoils 40 are physically arranged such that each has an equivalenteffective depth on the circuit assembly 30. That is, the windings arestacked within the circuit assembly 30 such that the average axialdistance from the magnets is maintained constant. For example, the firstlayer of coil A, winding 42 may be the most distant from the magnets,and the second layer of coil A, winding 48 the closest to the magnets,while the two layers of coil B winding 44 and winding 46 could besandwiched between the two layered windings of coil A. The exactconfiguration of the coil and winding arrangement stated is illustrativeonly, many configurations are possible and within the scope of theinvention. The key operative function is to minimize the effects ofmultiple winding effective distances (gaps) on the induced voltages.While two twelve turn windings are described, the coils need only beconfigured to allow adequate detection in light of the magnetic fieldstrength, processing employed, physical and operational constraints.

[0053]FIG. 3 depicts a partial view of a preferred embodiment. Threeturns of the first layer of coil A, winding 42 are shown. Each windingis comprised of six active segments 50 and six inactive segments 52 perturn. The active segments 50 are oriented approximately on radials fromthe center of the spiral while the inactive segments 52 are oriented asarcs of constant radius. The active segments 50 are strategicallypositioned equidistant about the circumference of the spiral anddirectly cutting the flux lines of the field generated by thelow-resolution magnet set 26. The inactive segments 52 are positioned atequal radial distances and are strategically placed to be outside themagnetic flux lines from the low-resolution magnet set 26. One skilledin the art will appreciate that the winding is uniquely configured asdescribed to provide maximum voltage generation with each passing poleof the low-resolution magnet set 26 in the active segments 50 andminimal or no voltage generation with each passing pole of thelow-resolution magnet 26 in the inactive segments 52. The abovementionedconfiguration results in predictable voltage outputs on the sense coils40 for each rotation of the low-resolution magnet set 26. A preferredembodiment employs two coils, on two layers each with 144 activesegments and 144 inactive segments. However, it will be understood thatonly the quantity of active segments 50 not the inactive segments 52 isrelevant. Any number of inactive segments 52 is feasible, only dictatedby the physical constraints of interconnecting the active segments 50.

[0054] Additionally, the sense coils 40 comprised two (or more) completespiral serpentine windings 42-48, 44-46. The sets of windings 42-48 and44-46 may be oriented relative to one another in such a way that thevoltages generated by the two sense coils 40 would possess differingphase relationships. For example by rotation of the sense coils 40relative to one another about the rotation axis 12. Further, it will beappreciated that, the orientation may be configured in such a way as tocause the generated voltages to be in quadrature. In a preferredembodiment where the low-resolution magnet set 26 comprises six magnetsof sixty degree segments, the two coils are rotated about the rotationaxis 12 concentrically relative to one another by thirty degrees. Thisrotation results in a phase difference of 90 degrees between the twogenerated voltages generated on each coil. In an exemplary embodiment,the two generated voltages are ideally configured such that the voltageamplitude is discernable for all positions and velocities. In anexemplary embodiment, the two generated voltages are substantiallytrapezoidal. FIG. 4 and FIG. 6 depicts the output voltage generated onthe two sense coils 40 as a function of rotation angle of the rotatingshaft 22 for a given speed.

[0055] In another embodiment of the invention, the windings may beindividually serpentine but not necessarily concentric. Again, the sensecoils 40 need only be configured to allow adequate detection in light ofthe magnetic field strength, processing employed, physical andoperational constraints. One skilled in the art would recognize that thecoil could be comprised of many other configurations of windings. FIG. 5depicts one such a possible embodiment.

[0056] Referring again to FIG. 1, in a preferred embodiment, the Hallsensor set 34 is located on the circuit assembly 30 in an orientationconcentric with the sense coils 40 and concentric with the rotating part20. Additionally, the Hall sensor set is placed at the same radius asthe active segments 50 of the sense coils 40 to be directly in lineaxially with the low-resolution magnet set 26 of the magnet assembly 24.The Hall sensor set 34 comprises multiple sensors equidistantlyseparated along an arc length where two such sensors are spacedequidistant from the sensor between them. In an exemplary embodiment,the Hall sensor set 34 includes, but is not limited to, three Halleffect sensors, 34 a, 34 b, and 34 c, separated by 40 degrees andoriented along the described circumference relative to a predeterminedreference position so that absolute rotational position of the rotatingpart 20 may be determined. Further, the Hall sensor set 34 is positionedto insure that the active segments 50 of the sense coils 40 do notinterfere with any of the Hall sensors 34 a, 34 b, and 34 c or viceversa. It is also noteworthy to consider that in FIG. 1, the Hall sensorset 34 is depicted on the distant side of the circuit assembly 30relative to the low-resolution magnet 26. This configuration representsa balancing trade between placing the Hall sensor set 34 or the sensecoils 40 closest to the low-resolution magnet set 26. In a preferredembodiment, such a configuration is selected because the signals fromthe Hall sensor set 34 are more readily compensated for the additionaldisplacement when compared to the voltages generated on the sense coils40. Conversely, in another embodiment, it may be desired to alter thedepicted configuration of the magnet assembly 24 and place the Hallsensor set 34 on the near side of the circuit assembly 30 in more directproximity to the sense coils 40 (as is depicted for the position sensor36). Such a configuration simplifies the depth of the apparatus and atthe same time facilitates placing other components on the distant sideof the circuit assembly 30 for example other circuit components,shielding, a flux concentrator and the like, including combinationsthereof. It will be appreciated by those skilled in the art thatnumerous variations on the described arrangement may be contemplated andwithin the scope of this invention. The Hall sensor set 34 detects thepassing of the low-resolution magnet set 26 and provides a signalvoltage corresponding to the passing of each pole. This provides aposition sensing functionality with the signal voltage accuratelydefining the absolute position of the rotational part 20. Again, in thepreferred embodiment, the three signals generated by the Hall sensor set34 with the six-pole low-resolution magnet facilitate processing byensuring that certain states of the three signals are never possible.One skilled in the art will appreciate that such a configurationfacilitates error and failure detection and ensures that the trio ofsignals always represents a deterministic solution for all possiblerotational positions.

[0057] The position sensor 36 is located on the circuit assembly 30 insuch an orientation as to be directly in line, axially with the magnetsof the outer annulus of the magnet assembly 24, yet outside the effectof the field of the low-resolution magnet set 26. The position sensor 36detects the passing of the high-resolution magnet set 28 and provides asignal voltage corresponding to the passing of each pole. To facilitatedetection at all instances and enhance detectability, the positionsensor 36 includes, but is not limited to, two Hall effect sensors in asingle package separated by a distance equivalent to one half the widthof the poles on the high-resolution magnet set 28. Thus, with such aconfiguration the position signals generated by the position sensor 36are in quadrature. One skilled in the art will appreciate that thequadrature signal facilitates processing by ensuring that one of the twosignals is always deterministic for all possible positions. Further,such a signal configuration allows secondary processing to assess signalvalidity. FIG. 6 depicts the output voltage as a function of rotationalangle of the position sensor 36 for a given speed. It is noteworthy topoint out that the processing of the high-resolution position allowsonly a relative determination of rotational position. It is however,acting in conjunction with the information provided by thelow-resolution position signals from the Hall sensor set 34 that adetermination of the absolute position of the rotating part 20 isachieved. Other applications of the low-resolution position sensor arepossible.

[0058] In another embodiment of the invention, the structure describedabove is constructed in such a fashion that the active segments of thesense coils 40 are at a radial proximity to the magnet assembliesinstead of axial. In such an embodiment, the prior description isapplicable except the rotational part 20 includes magnets that arecoaxial but not coplanar and are oriented such that their magneticfields radiate in the radial direction rather than the axial direction.Further, the circuit assembly 30 may be formed cylindrically rather thanplanar and coaxial with the rotational part 20. Finally, the sense coils40, Hall sensor set 34, and position sensor 36, are oriented such thatthe active segments 50 are oriented in the axial direction in order todetect the passing magnetic field of the low-resolution magnet set 26.

[0059] Apparatus and Structure: Sinusoidal Response

[0060] In yet another embodiment, a modification to the abovementionedsense coils 40 is disclosed. This alternative embodiment provides atachometer coil 40 configuration that yields a sinusoidal inducedvoltage and output response. A sinusoidal response characteristicincludes the inherent benefit of facilitating accurate processing of theinduced voltages.

[0061] Referring once again to FIGS. 1 and 2, and now referring as wellto FIG. 14, the sense coils 40 may once again be located on the circuitassembly 30 in such an orientation as to be concentric with the magnetassembly 24 in close proximity to the inner annulus low-resolutionmagnet set 26. Also in this embodiment, the sense coils 40 areconductive and an integral part of the circuit interconnection 38.Furthermore, in this embodiment, the sense coils 40 include two or morespiraling conductor coils 42-48 concentrically wound about the rotationaxis 12 in a serpentine fashion such that each conductor includes, butis not limited to, a 16 turn winding comprised of 8 turns on each of twolayers. Coil A is comprised of windings 42 and 48 and coil B iscomprised of windings 44 and 46. Each of the windings is configured suchthat it spirals inward toward the rotation axis 12 on one layer andoutward from the rotation axis 12 on the second layer. Thereby, theeffects of the windings' physical construction variances on the inducedvoltages are minimized. Further, the sense coils 40 are physicallyarranged such that each has an equivalent effective depth on the circuitassembly 30. That is, the windings are stacked within the circuitassembly 30 such that the average axial distance from the magnets ismaintained constant. For example, the first layer of coil A, winding 42could be the most distant from the magnets, and the second layer of coilA, winding 48 the closest to the magnets, while the two layers of coil B44 and 46 could be sandwiched between the two layered windings of coilA. Finally, in distinction to the abovementioned embodiments, the sensecoils 40 are arranged on the circuit assembly 30 with a configuration toensure that substantially a fundamental frequency of a sinusoid isproduced and the harmonics of that fundamental frequency are cancelled.In particular, for each winding 42, 48 of coil A and 44, 46 of coil B,particular conductors are pivoted about the rotation axis 12 of thepoles by a selected angular displacement. Once again, the exactconfiguration of the coil and winding arrangement stated is illustrativeonly, many configurations are possible and within the scope of theinvention. The operative functionality being minimizing the effects ofmultiple winding effective distances (gaps) on the induced voltages.While two sixteen turn coils are described, the sense coils 40 need onlybe configured to allow adequate detection in light of the magnetic fieldstrength, processing employed, physical and operational constraints.

[0062]FIG. 14 depicts a view of this alternative embodiment. In anembodiment, eight turns of the first layer of coil A, winding 42 areshown. Each winding is comprised of six active segments 50 and sixinactive segments 52 per turn. The active segments 50 are orientedapproximately on radials from the center of the spiral while theinactive segments 52 are orientated as arcs of constant radius. Theactive segments 50 are strategically positioned about the circumferenceof the spiral and directly cutting the flux lines of the field generatedby the low-resolution magnet set 26. The inactive segments 52 arepositioned at substantially equal radial distances and are strategicallyplaced to be outside the magnetic flux lines from the low-resolutionmagnet set 26, thereby ensuring that no voltage is induced in theinactive segments 52. Also unique to this alternative embodiment, isthat each conductor of the active segments 52 for a respective turn ofthe eight turns is pivoted concentrically about the rotation axis 12 bya selected number of degrees. More specifically, in an exemplaryembodiment including two sense coils 40, each comprising two windings,one on each of two layers. Considering each turn of a respective winding(e.g. 42, 44, 46, 48), each of the active segments 50 of the eight turnsis pivoted concentrically about the rotation axis 12 by a selectednumber of degrees of angular displacement from a center of a pole 16.The center of the pole being an arbitrarily selected reference point formeasurement and alignment between the sense coils 40 and thelow-resolution magnet set 26 generally characterized as the center of apole of the low-resolution magnet set 26 placed at a particularrotational orientation. In an embodiment, six pole centers correspondingto the six poles of the low-resolution magnet set 26 are utilized fordescriptive references of the layout of the sense coils 40. It isevident that other referencing entities and methods are possible.Referring to FIG. 14, the horizontal axis 14 indicates the pole center16 for a first pole the remaining poles and respective pole centers 16are spaced equidistant at 60-degree intervals counterclockwise about therotation axis 12.

[0063] The rotation described above results in a winding configurationthat facilitates maximum fundamental voltage generation and yetcancellation of the third, fifth, and seventh harmonics. FIG. 15 depictsa table and a vector diagram that illustrates the addition of theindividual contributions from the active segments 50 to the overallvoltage generated. FIG. 15A depicts the vector diagram for thefundamental frequency. FIG. 15B depicts the vector diagram for the thirdharmonic. Finally, FIG. 15C depicts the vector diagram for the fifthharmonic. It will be evident that the contributions to the fundamentalfrequency are additive, while in the case of the third and fifthharmonic, the contributions from the individual active segments 50 areoriented such that they cancel one another. To effect the cancellationof the seventh harmonic, it is desirable to orient the windings suchthat the contributions for the seventh harmonic cancel. To effect such acancellation, one winding of each of the winding pairs that comprise thesense coils is rotated relative to the other winding. In an exemplaryembodiment, the rotation is by 8.57 degrees from one winding on onelayer to the other winding on another layer. For example, for coil A ofthe sense coils 40, winding 48 may be rotated in its entirety about therotation axis 12 relative to winding 42. Likewise for coil B and winding44 and winding 46. FIG. 16 depicts two windings (e.g. 42 and 48) of onetachometer coil 40 with rotation for seventh harmonic cancellation. Itis noteworthy to recognize that this rotation of 8.57 degreescorresponds to half the wavelength of the frequency that is to beeliminated. In an exemplary embodiment, the seventh harmonic correspondsa wavelength of 51.4 electrical degrees, half of which would be 25.7degrees. It should be noted that the 25.7 electrical degrees correspondsto 8.57 mechanical degrees for a three-pole pair electric machine.Therefore, with the rotation of one of the two windings for eachtachometer coil 40 the seventh harmonic components induced on onewinding are out of phase with the same components induced on the otherwinding and thus cancel when summed.

[0064] To illustrate further, an exemplary embodiment is depicted inFIG. 14 for one winding (e.g. 42, 44, 46, 48) of one of the sense coils40. In the figure, the horizontal axis 14 indicates the pole center 16for a first pole, the remaining poles and respective pole centers 16 arespaced equidistant at 60-degree intervals counterclockwise about therotation axis 12. The active segment 50 for a particular turn of thewinding (e.g. 42, 44, 46, 48) will be oriented as defined in Table 1 andalternating for each subsequent pole. For example, for the outermostturn (conductor 1) the first active segment 50 a will be located −18degrees (clockwise) from the pole center 16 a at the horizontal axis 14and the second active segment 50 b will be at +18 degrees from thesecond pole center 16 b at 60 degrees or 78 degrees counter clockwisefrom the horizontal axis. Moreover, the third active segment 50 c willbe at −18 degrees from the third pole center 16 c another 60 degreescounterclockwise or 102 degrees from the horizontal axis 14. Inaddition, the fourth active segment 50 d will be +18 degrees from thefourth pole center 16 d or 198 degrees counterclockwise from thehorizontal axis. Likewise, the fifth active segment 50 e will be −18degrees from the fifth pole center 16 e or 228 degrees counterclockwisefrom the horizontal axis. Finally, to complete the turn, the sixthactive segment 50 f will be +18 degrees from the sixth pole center 16 for 318 degrees counterclockwise from the horizontal axis. Active SegmentDegrees Offset Degrees Offset Conductor # (at Horizontal Axis)(Subsequent Pole) 1 −18 +18 2 −14 +14 3 −6 +6 4 −2 +2 5 +2 −2 6 +6 −6 7+14 −14 8 +18 −18

[0065] Continuing along the same concept for the second to outermostturn (conductor 2), the active segments 50 will be at −14 and +14degrees from the respective pole centers 16 a, 16 b, 16 c, 16 d, 16 e,and 16 f. Ultimately concluding with the innermost turn (conductor 8)with the active segments placed at −18 degrees from each of the polecenters 16 a, 16 b, 16 c, 16 d, 16 e, and 16 f respectively. It isnoteworthy to appreciate at this time that the inactive segments 52 areconfigured and arranged as described earlier and merely provided theelectrical interconnection among the active segments 50.

[0066] Once again it will appreciated that each winding is uniquelyconfigured as described to provide maximum voltage generation with eachpassing pole of the low-resolution magnet set 26 in the active segments50 and minimal or no voltage generation with each passing pole of thelow-resolution magnet set 26 in the inactive segments 52. This resultsin predictable voltage outputs on the sense coils 40 for each rotationof the low-resolution magnet set 26. A exemplary embodiment employs twocoils, on two layers each with 96 active segments 50 and 96 inactivesegments 52. However, it will be understood that only the quantity ofactive segments 50 not the inactive segments 52 is relevant. Any numberof inactive segments 52 is feasible, only dictated by the physicalconstraints of interconnecting the active segments 50.

[0067] Similarly, the sense coils 40 are once again comprised of two (ormore) complete spiral serpentine windings 42-44, 46-48. The windings42-48 and 44-46 may be oriented relative to one another in such a waythat the voltages generated by the two sense coils 40 would possessdiffering phase relationships. Further, it will be appreciated that theorientation may be configured in such a way as to cause the generatedvoltages to be in quadrature. In a preferred embodiment where thelow-resolution magnet set 26 includes, but is not limited to, sixmagnets of sixty degree segments, the two sense coils 40 are rotatedconcentrically relative to one another by thirty degrees. This rotationresults in a phase difference of 90 degrees between the two generatedvoltages generated on each coil. In an exemplary embodiment, the twogenerated voltages are ideally configured such that the voltageamplitude is discernable for all positions and velocities. Moreover, inan exemplary embodiment by way of the configuration of the sense coils40 the voltages generated are essentially sinusoidal. FIG. 17 depictsthe four windings 42, 48, and 44, 46 of the two sense coils 40 overlaidfor completeness. It should be appreciated once again, that the exactconfiguration of the coil and winding arrangement stated is illustrativeonly, many configurations are possible and within the scope of theinvention. The operative functions need only be addressed in light ofthe configuration selected. For example, to minimize the effects ofmultiple winding effective distances (gaps) on the induced voltages, orto cancel induce harmonics. While two eight turn windings on two layersare described, other configurations may be possible, the coils need onlybe configured to allow adequate detection and harmonic cancellation inlight of the magnetic field strength, number of pole pairs, processingemployed, physical and operational constraints.

[0068] Apparatus and Structure: Interference Cancellation

[0069] Turning now to yet another alternative embodiment, disclosedherein is an enhancement to the tachometers identified in theabovementioned embodiments. In this embodiment, the orientation of thesense coils 40 is configured to avoid susceptibility to externalmagnetic field disturbances. Referring to FIG. 18 a simplified view ofjust two turns of two windings e.g., 42 and 48 or 44 and 46 thatcomprise a tachometer coil 40 (FIG. 3) are depicted. In theabovementioned embodiments the two windings that comprise coil A and thetwo windings e.g., 44 and 46 that comprise coil B of the sense coils 40are substantially in phase combining their respective inducedcomponents. The resultant of which, is that the voltages induced in eachof the windings (e.g., 42 and 48 or 44 and 46) are directly summed andadditive. Therefore, in the presence of an external magnetic field, eachwinding is substantially equally affected resulting in the additivecombination of any induced voltage resultant from an external magneticfield. To avoid this effect an alternative embodiment is disclosed,which reconfigures the sense coils 40 to minimize and cancel such anundesirable effect.

[0070] Referring to FIG. 19, the same two windings (e.g., 42 and 48 or44 and 46) are shown, however, in this embodiment, the windings arepivoted about the rotation axis 12 relative to one another in a mannerthat results in common mode cancellation when the voltages induced oneach of the windings are summed. In an exemplary embodiment, thewindings are arranged such that they are 60 degrees rotated from oneanother. More particularly, as is shown in FIG. 13, a winding (e.g., 48)on one layer is pivoted about the rotation axis 12 relative to the otherwinding (e.g., 42) on another layer. Such a configuration permits atparticular instances, one winding (e.g., 42) to be aligned with onepolarity magnet (e.g., a north pole) of the low-resolution magnet set 26while the other winding (e.g., 48) of the pair comprising a tachometercoil 40 is aligned with the opposite polarity magnet (e.g., a southpole) of the low-resolution magnet set 26. Moreover, the pivoted winding(e.g., 48), in this exemplary embodiment, is wound in the oppositedirection than the direction that the winding 42 is wound. That is, onewinding is wound clockwise while the other is wound andcounterclockwise. Also unique to this embodiment, and unlike theabovementioned embodiments is that here the windings (e.g., 42, and 48)may be wound spiraling in the same direction. For example, one windinge.g., 42 is wound spiraling inward clockwise on one layer while theother winding e.g., 48, is wound spiraling inward and counterclockwiseon another layer. Such a configuration causes the combined contributionsto the induced voltages from the coils to accumulate the contributionsfrom the active segments 50 as they pass the low-resolution magnet set26, while simultaneously canceling the contributions from the inactivesegments 52. This effect on the induced voltage is accomplished because,in this embodiment, the low-resolution magnet set 26 and active segments50 are at 60 mechanical degree intervals. The 60-degree rotation of onewinding e.g., 48, results in an effective phase reversal (180 degreeselectrical) of the two windings (e.g., 42, and 48), or more particularlythe voltage induced on the two windings (e.g., 42, and 48) from theactive segments 50. That is the voltages induced by the active segments50 on the windings 42, and 48 respectively substantially cancel.However, the change in the direction of winding for one winding e.g., 48versus the other e.g., 42 imparts an additional phase reversal for theactive segments 50 and a phase reversal for the inactive segments 52.Thereby causing the active segments 50 to once again, all exhibit inphase voltages, while the inactive segments 52 contributions remain outof phase. Thus, causing the resultant voltage output of the windings 42and 48 to yield an induced voltage, including the cumulativecontributions of the active segments, and yet cancel the contributionsof voltages induced on the inactive segments 52 due to external fields.It should be evident that a particular direction of winding and spiralare not essential for one winding e.g., 48 versus the other e.g., 42.The windings (e.g., 42, and 48) need only be wound such that, thecontribution to the induced voltage is cumulative for the activesegments 50 and canceling for the inactive segments 52.

[0071] In yet another variation to the above alternative embodiment,referring to FIG. 20, the implementation of the interferencecancellation techniques disclosed may be implemented in a more evidentapproach. Another coil denoted a cancellation coil 80, substantiallycircular and coaxial with the sense coils 40, and more particularly, theinactive segments 52, may be employed. A cancellation coil 80 maycomprise substantially the same number of turns as the sense coils 40wound in the opposite direction of the sense coils 40 with an averagediameter substantially equivalent to the average diameter of the sensecoils 40. Such a cancellation coil 80, like the inactive segments 52 isconfigured to be insensitive to the magnetic flux from thelow-resolution magnet set 26, and yet responsive to the flux fromexternal magnetic fields. When a cancellation coil 80 is placed incombination, (in an embodiment, in series) with the sense coils 40 thevoltages induced on the combination of coils will include thecontributions from the active segments 50, in response to the magneticflux from the low-resolution magnet set 26, yet not include the effectsof external magnetic fields on the inactive segments 52. The effects ofexternal magnetic fields on the inactive segments 52 will be cancelledby the voltage induced upon the cancellation coil 80.

[0072] Once again it should be noted, that the exact configuration ofthe coil and winding arrangement stated is illustrative only, manyconfigurations are possible and within the scope of the invention. Theoperative functions need only be addressed in light of the configurationselected. For example, in the abovementioned embodiment, to minimize theeffects external magnetic fields on the induced voltages, or to cancelinduce harmonics. While two eight turn windings (e.g., 42 and 48) on twolayers are described, other configurations may be possible, the coils(40) need only be configured to allow adequate detection, harmoniccancellation and external field cancellation in light of the magneticfield strength, number of pole pairs, processing employed, physical andoperational constraints. Moreover, it is noteworthy to recognize thatthe cancellation coils 80 may be configured as additional circuit traceson the circuit interconnection 38 of the circuit assembly 30 or asindependent coils of another discrete component.

[0073] Apparatus and Structure—Combined Sinusoidal and InterferenceCancellation

[0074] It is evident that the apparatus disclosed earlier for theinterference cancellation configuration of the sense coils 40 may beutilized with the configuration of sense coils 40 providing atrapezoidal response or a sinusoidal response. FIGS. 18-20 illustratetachometer coil 40 comprising windings (e.g., 42, 48, and 44, 46) forthe combination with a trapezoidal response, while FIGS. 21-24 depictthe tachometer coil 40 comprising windings (e.g., 42, 48, and 44, 46)with sinusoidal response combined with the interference cancellation. Itis noteworthy to appreciate that these configurations are illustrative,and that there may be other combinations of configurations possible andwithin the scope of this disclosure and yet not specifically enumeratedhere.

[0075] Signal Processing; Trapezoidal

[0076]FIG. 7 depicts the top-level block diagram of the processingfunctions employed on the various signals sensed to determine therotational speed of a rotating device. The processing defined would betypical of what may be performed in a controller 90. Such a controller90 may include, without limitation, a processor, logic, memory, storage,registers, timing, interrupts, and the input/output signal interfaces asrequired to perform the processing prescribed by the invention. Thecontroller 90 receives as input signals two signals indicative of thevelocity rotating device from the tachometer structure 10 and a positionsignal generated by the high resolution position sensor 36. Referringagain to FIG. 7, where the blocks 100-1000 depict the adaptive algorithmexecuted by the abovementioned controller 90 in order to generate thetachometer output. The first four blocks 100, 200, 400, 600 perform the“forward” processing of the tachometer coil signals to arrive at thefinal blended output. While, the last two 800, 1000 comprise a“feedback” path thereby constructing the adaptive nature of thealgorithm.

[0077] In FIG. 7, the function labeled Speed Estimation 100 generates adigital, derived velocity signal. The process utilizes Motor_Position_HRthe high-resolution position sensed by the high resolution positionsensor 36, and a processor clock signal for timing. The process outputsa signal Motor_Vel_Der_144, which is proportional to the velocity of themotor over the sample period of the controller. Continuing to OffsetCompensation 200 where processing is performed to generate filteredtachometer signals to remove offsets and bias. The process utilizes thetwo tachometer coil signals HallTachVoltX1, HallTachVoltX2, the derivedvelocity Motor_Vel_Der_144 and two phase related feedback signalsint_Phase0 and int_Phase1 as inputs and generates corrected velocityoutputs X1_Corr and X2_Corr. Continuing to Get Phase 400 whereprocessing is performed to ascertain magnitude and phase relationshipsof the two corrected velocities. Inputs processed include the correctedvelocities X1_Corr, X2_Corr, and the motor position Motor_Position_SPIas derived from the high-resolution position detected by sensor 36. Theprocess generates two primary outputs, the selected tachometer magnitudetach_vel_mag and the selected tachometer phase tach_vel_sign. Moving tothe Blend 600 process, predetermined algorithms determine a blendedvelocity output. The process utilizes the selected tachometer magnitudetach_vel_mag and the selected tachometer phase tach_vel_sign to generatetwo outputs; the blended velocity Blend_Vel_Signed and the velocity signOutputSign. Considering now the Align to Polled 800 process wherein thetachometer magnitude tach_vel_mag is time shifted based upon themagnitude of the derived velocity Motor_Vel_Der_144. The selected signalis filtered and supplied as an output as Filtered_Tach. Finally, lookingto Gain 1000 where the process generates an error command resultant fromthe difference between the derived velocity and filtered tachometerunder predetermined conditions. The error signal is integrated andutilized as an error command signal for gain adjustment feedback Theprocess utilizes the derived velocity Motor_Vel_Der_144 and theFiltered_Tach signal as inputs to generate two outputs int_Phase0 andint_Phase1. These two signals form the gain adjustment feedback that isthen utilized as an input in the abovementioned Offset Compensation 200.

[0078] Referring now to FIG. 7 and FIGS. 8A and 8B for a more detaileddescription of the functional operation of each of the processesidentified above. FIG. 8A depicts the functions that comprise the SpeedEstimation 100 process block. FIG. 8B provides a more detailed depictionof an exemplary embodiment for the Deltact Calculation process 102 and aDigital Filter 104. This process is a method of extracting a digital,derived velocity based on the per sample period of change of theposition signal. The process utilizes as an input Motor_Position_HR thehigh-resolution position detected by sensor 36, and outputs a signalMotor_Vel_Der_144, which is proportional to the derived velocity of themotor. The process computes the velocity by employing two mainfunctions. The first is the Deltact calculation process 102 where aposition change DELTA_POS is computed by subtracting the high-resolutionposition Motor_Position_HR delayed by one sample from the currenthigh-resolution position Motor_Position_HR. That is, subtracting thelast position from the current position. The position difference is thendivided by the difference in time between the two samples. An equationillustrating the computation is as follows:${Deltact} = \frac{P_{0} - P_{- 1}}{T_{0} - T_{- 1}}$

[0079] A preferred embodiment of the above equation evaluates a changingmeasured position over a fixed interval of time to perform thecomputation. It will be appreciated by those skilled in the art, thatthe computation may be performed with several variations. An alternativeembodiment, evaluates a changing measured time interval for a fixedposition change to perform the computation. Further, in yet anotherembodiment, both the interval of time and interval position could bemeasured and compared with neither of the parameters occurring at afixed interval.

[0080] A filter 104 further processes the calculated Deltact value.Where the filtering characteristics are selected and determined suchthat the filter yields a response sufficiently representative of thetrue velocity of the motor without adding excessive delay. One skilledin the art will appreciate and understand that there can be numerouscombinations, configurations, and topologies of filters that can satisfysuch requirements. A preferred embodiment employed a four-state movingaverage filter. The signal is labeled Motor_Vel_Der, which is thenscaled at gain 106 and output from the process as the value labeledMotor_Vel_Der_144. This parameter is utilized throughout the inventionas a highly accurate representation of the velocity.

[0081]FIG. 9 depicts the functions that comprise the Offset Compensationprocess 200. The process extracts the respective offset and bias fromeach of the two tachometer coil signals HallTachVoltX1 andHallTachVoltX2 resulting in corrected velocity outputs X1_Corr andX2_Corr. The extraction is accomplished by an algorithm that underpredetermined conditions subtracts from each of the tachometer signalsits low frequency spectral components. The algorithm is characterized byscaling 202; a selective, adaptive, filter 204; and a gainschedule/modulator Apply Gain 210. Where, the scaling 202 provides gainand signal level shifting resultant from the embodiment with an analogto digital conversion; the adaptive filter 204 comprises dual selectivelow pass filters 206 and summers 208 enabled only when the tachometersignals' levels are valid; and gain scheduling, which is responsive tofeedback signals int_Phase0 and int_Phase1 from the Gain process 1000.

[0082] The adaptive filter 204 is characterized by conditionally enabledlow pass filters 206, and summers 208. The low pass filters 206 underestablished conditions are activated and deactivated. When activated,the filter's 206 results are the low frequency spectral content of thetachometer signals to a predetermined bandwidth. When deactivated, thefilter 206 yields the last known filter value of the low frequencyspectral content of the tachometer signals. It is important to considerthat the filter 206 is activated when the tachometer signals are validand deactivated when they are not. In a preferred embodiment, thisoccurs when the tachometer signals saturate at a high velocity. Variousconditions may dictate the validity of the tachometer signals. In apreferred embodiment, within certain hardware constraints, to satisfylow speed resolution and bandwidth requirements, high speed sensingcapability with the tachometer signals is purposefully ignored. Thisresults in the tachometer signals saturating under high speed operatingconditions. As such, it is desirable to deactivate the filters 206 undersuch a condition to avoid filtering erroneous information. A summer 208subtracts the low pass filter 206 outputs to the original tachometersignals thereby yielding corrected tachometer signals with the steadystate components eliminated. The filter 206 characteristics areestablished to ensure that the filter response when added to theoriginal signals sufficiently attenuates the offsets and biases in thetachometer signals. One skilled in the art will appreciate that therecan be numerous combinations, configurations, and topologies of filtersthat can satisfy such requirements. A preferred embodiment employs anintegrating loop low pass filter.

[0083] The gain scheduling function Apply Gain 210 is responsive tofeedback signals int_Phase0 and int_Phase1 from the Gain process 1000(discussed below). The Apply Gain 210 process scales the correctedvelocity outputs X1_Corr and X2_Corr as a function of the feedbacksignals int_Phase0 and int_Phase1. Thereby providing a feedbackcontrolled correction of the velocity signal for accuracy and speedcorrection.

[0084]FIG. 10 depicts the internal process of Get Phase 400 whereprocessing is performed to ascertain magnitude and phase relationshipsof the two corrected velocities. Inputs processed include the offsetcorrected velocities X1_Corr, X2_Corr, the motor positionMotor_Position_SPI, and a calibration adjustment signal TachOffset. Themotor position signal Motor_Position_SPI derived from thehigh-resolution position as detected by sensor 36 and indexed to theabsolute position as described earlier. The TachOffset input allows foran initial fabrication based adjustment to address differences orvariations in the orientation of the sense coils 40 (FIGS. 1 and 3) andthe low-resolution Hall sensor set 34 (FIG. 1). The process generatestwo primary outputs, the selected tachometer magnitude tach_vel_mag andthe selected tachometer phase tach_vel_sign. The process independentlydetermines which tachometer signal magnitude and phase to select bymaking a comparison with the high-resolution positionMotor_Position_SPI. The process determines the magnitude of the twovelocities X1_Corr and X2_Corr at 402. Then at comparator 404 determinesthe larger of the two and then generates a discrete, Phase_Sel,indicative of which velocity has the larger magnitude. The largermagnitude velocity is selected because by the nature of the twotrapezoidal signals, one is guaranteed to be at its maximum. Thediscrete Phase_Sel controls a switch 406, which in turn passes theselected tachometer velocity magnitude termed tach_vel_mag. The discretePhase_Sel is also utilized in later processes. A second and separatecomparison at Get Sign process 408 with the high-resolution positionMotor_Position_SPI, extracts the respective sign associated with thevelocity. Again, it will be understood that those skilled in the art mayconceive of variations and modifications to the preferred embodimentshown above. For example, one skilled in the art would recognize thatthe phase information could have also been acquired merely by utilizingthe position information alone. Such an approach however, suffers inthat it would be highly sensitive to the precise positioning and timingon the trapezoidal waveforms to insure an accurate measurement. Such arestriction is avoided in the preferred embodiment, thereby simplifyingthe processing necessary.

[0085]FIG. 11 depicts the Blend 600 process function where predeterminedalgorithms determine a blended velocity output. The process utilizes theselected tachometer magnitude tach_vel_mag, the derived velocityMotor_Vel_Der_144 and the selected tachometer phase tach_vel_sign togenerate two outputs; the blended velocity Blend_Vel_Signed and thevelocity sign OutputSign. A blended velocity solution is utilized toavoid the potential undesirable effects of transients resultant fromrapid transitions between the derived velocity and thetachometer-measured velocity. The process selects based upon themagnitude of the derived velocity Motor_Vel_Der_144 a level ofscheduling at gain scheduler 602 of the derived velocity with thecompensated, measured, and selected velocity, tach_vel_mag. Summer 604adds the scheduled velocities, which are then multiplied at multiplier606 by the appropriate sign as determined from the tachometer phasetach_vel_sign to generate the blended composite signal. The blendedcomposite signal comprises a combination of the tachometer measuredvelocity and the derived velocity yet without the negative effects ofsaturation or excessive tine delays.

[0086]FIG. 12 depicts the Align to Polled 800 process, which time shifts(delays) the tachometer magnitude tach_vel_mag to facilitate a coherentcomparison with the derived velocity Motor_Vel_Der_144. The filtering isonly employed when the tachometer magnitude tach_vel_mag is within avalid range as determined in processes 802 and 804. The valid range isdetermined based upon the magnitude of the derived velocityMotor_Vel_Der_144. As stated earlier, the validity of the tachometersignals is related to high speed saturation, while for the derivedvelocity it is a function of filtering latency at very low speed. Aselection switch 804 responsive to the magnitude of the derived velocityMotor_Vel_Der_144 controls the application of the tach_vel_mag signal tothe filter. The multiplication at 808 multiplier applies the appropriatesign to the tach_vel_mag signal. A filter 806 is employed to facilitategeneration of the time delay. The appropriate time delay is determinedbased upon the total time delay that the derived velocity signalsexperience relative to the tachometer signals. The time shift accountsfor the various signal and filtering effects on the analog signals andthe larger time delay associated with filtering the derived velocitysignal. As stated earlier, the derived velocity signal experiences asignificant filtering lag, especially at lower speeds. Introducing thisshift yields a result that makes the tachometer signals readilycomparable to the derived velocity. The selected signal is delivered asan output as Filtered_Tach.

[0087] In a preferred embodiment, the resultant filter 806 is a fourstate moving average filter similar to the filter 104 (FIG. 8)implemented in the Speed Estimation process. One skilled in the art willrecognize that there can be numerous combinations, configurations, andtopologies of filters that can satisfy such requirements.

[0088] Referring now to FIG. 13, the Gain 1000 process block where anerror command is generated and subsequently utilized as a gaincorrection in the adaptive algorithm of the present invention. In apreferred embodiment, the error command is resultant from a ratiometriccomparison 1002 of the magnitudes of the derived velocity to thefiltered tachometer velocity. The ratio is then utilized to generate anerror signal at summer 1004. Under predetermined conditions, controlledby state controller 1006, error modulator 1008 enables or disables theerror signal. That is, modulator 1008 acts as a gate whereby the errorsignal is either passed or not. The state controller 1006 allows theerror signal to be passed only when the error signal is valid. Forexample, when both the filtered tachometer velocity and the derivedvelocity are within a valid range. In a preferred embodiment, the errorsignal is passed when the magnitude of the Motor_Vel_Der_144 signal isbetween 16 and 66.4 radians per second. However, the modulator isdisabled and the error signal does not pass if the magnitude of theMotor_Vel_Der_144 signal exceeds 72 or is less than 10.4 radians persecond. Under these later conditions, the ratiometric comparison of thetwo velocities and the generation of an error signal is not valid. Atvery small velocities, the signal Motor_Vel_Der_144 exhibits excessivedelay, while at larger velocities, that is in excess of 72 radians persecond, the tachometer signals are saturated. The error signal whenenabled is passed to the error integrator 1010, is integrated, and isutilized as an error command signal for gain adjustment feedback. Theerror integrators 1010 selectively integrate the error passed by themodulator 1008. The selection of which integrator to pass the errorsignal to is controlled by the time shifted Phase_Sel signal at delay1012. These two correction signals; int_Phase0 and int_Phase1, form thegain adjustment feedback that is then utilized as an input in theabovementioned Offset Compensation 200 process.

[0089] Signal Processing; Sinusoidal

[0090]FIG. 25 depicts the top-level block diagram of the processingfunctions employed on the various signals sensed to determine therotational speed of a rotating device. The processing defined would betypical of what may be performed in a controller. Such a controller mayinclude, without limitation, a processor, logic, memory, storage,registers, timing, interrupts, and the input/output signal interfaces asrequired to perform the processing prescribed by the invention.Referring again to FIG. 25, where the blocks 1100-1900 depict anadaptive algorithm executed by the abovementioned controller in order togenerate the tachometer output. The four blocks 1100, 1200, 1400, 1500and 1600 perform “forward” processing of the tachometer coil signals toarrive at a final blended output. While, the last two 1700, and 1800comprise a “feedback” path thereby constructing the adaptive nature ofthe algorithm.

[0091] In FIG. 26, the function labeled Speed Estimation 1100 generatesa digital, derived velocity signal. Similar to earlier disclosedembodiments (see FIGS. 7, 8A and 8B), the process utilizesMotor_Position_HR, the high-resolution position from sensor 36, and aprocessor clock signal for timing. The process outputs a signalMotor_Vel_Der_144, which is proportional to the velocity of the motorover the sample period of the controller. Continuing to OffsetCompensation process 1200 where processing is performed to generatefiltered tachometer signals to remove offsets and bias. The OffsetCompensation process 1200 utilizes the two tachometer coil signalsHallTachVoltX1, HallTachVoltX2, the derived velocity Motor_Vel_Der_144and two phase related feedback signals ADJ_GAIN_1 and ADJ_GAIN_2 asinputs and generates corrected velocity outputs X1_Corr and X2_Corr.Also output from the Offset Compensation process 1200 are twouncorrected velocity outputs X1 and X2. Continuing to Phase andMagnitude process 1400, the magnitude and phase relationships of the twocorrected velocities are determined. Inputs processed include the twouncorrected velocity outputs X1 and X2, the corrected velocitiesX1_Corr, X2_Corr, the motor position Motor_Position_SPI as derived fromthe high-resolution position detected by sensor 36, and an alignment oroffset constant denoted in the figure as k_tach_align. The processgenerates four primary outputs, the selected tachometer magnitudetach_vel_mag; the selected tachometer phase tach_vel_sign; and two phaseenable discretes Phase_A_En; and Phase_B_En. Moving to the Apply GainFunction 1500 where gain scaling sign are applied to the selectedtachometer magnitude, tach_vel_mag. Inputs to the Apply Gain process1500 include: the selected tachometer magnitude tach_vel_mag; theselected tachometer phase tach_vel_sign; a magnitude gain utilized toschedule the tachometer magnitude tach_vel_mag, MAG_GAIN. Output fromthe Apply Gain process 1500 is the scaled and signed tachometer velocitydenoted TACH_VELOCITY_HR. Finally, the Velocity Blend process 1600 whereselected algorithms determine a blended velocity output denoted asBLEND_VELOCITY_HR. The process utilizes the scaled and signed tachometervelocity TACH_VEL_HR and the derived tachometer velocityMotor_Vel_Der_144, to generate the blended velocity BLEND_VEL_HR. Movingto the “feedback” portion of the algorithm, the Auto-Gain Calculationprocess 1700 wherein two gain corrections are computed for laterscheduling and application as gain adjustments to the two uncorrectedvelocity outputs X1 and X2. The process utilizes the derived velocityMotor_Vel_Der 144, the TACH_VELOCITY_HR signal, the Phase_A_En andPhase_B_En to generate two gain correction factors GAIN_1 and GAIN_2.

[0092] Moving now to a Dynamic Gain Adjust process, 1800 to formulatetwo gain adjustment outputs ADJ_GAIN_1; ADJ_GAIN_2; and a magnitude gaincommand MAG_GAIN which, are resultant of scheduling of the two gaincorrection factors GAIN_1 and GAIN_2. The two signals form the gainadjustment feedback that is utilized as an input in the abovementionedOffset Compensation 200.

[0093] Referring now to FIG. 25 and specified figures for a detaileddescription of the functional operation of each of the processesidentified above. FIG. 26 depicts the functions that comprise the SpeedEstimation 1100 process block. This process is a method of extracting adigital, derived velocity based on the per sample period of change ofthe position signal. The Speed Estimation 1100 process calculates motorvelocity based on differentiating changes in motor position. Theprocessing employed herein is similar to that discussed in theembodiments disclosed above, and specifically at the Speed Estimation100 process as depicted in FIGS. 8A and 8B. Therefore, for simplicity,the disclosure is not reiterated here.

[0094]FIG. 27 depicts the functions that comprise the OffsetCompensation process 1200. The process extracts the respective offsetand bias from each of the two tachometer coil signals HallTachVoltX1 andHallTachVoltX2 resulting in two uncorrected velocity outputs X1 and X2.The Offset Compensation process 1200 also includes, but is not limitedto, an Apply Gain process 1210 configured to receive the gainadjustments ADJ_GAIN_1 and ADJ_GAIN_2 and therefrom generate correctedvelocity outputs X1_Corr and X2_Corr. It is noteworthy to appreciatethat the Offset Compensation process 1200 is very similar to the OffsetCompensation process 200 disclosed in earlier embodiments. Reference maybe made to that disclosure above herein for additional details.

[0095] The extraction of offsets and biases from each of the twotachometer coil signals HallTachVoltX1 and HallTachVoltX2 isaccomplished by an algorithm that under selected conditions subtractsfrom each of the tachometer signals its low frequency spectralcomponents. The algorithm and processing employed shown in FIG. 27 ischaracterized by scaling 202; a selective, adaptive, filter 204; and again schedule/modulator Apply Gain process 1210. Where, the scaling 202provides gain and signal level shifting resultant from the embodimentwith an analog to digital conversion; the adaptive filter 204 comprisesdual selective low pass filters 206 and summers 208 enabled only whenthe tachometer signals levels are valid; and gain scheduling, which isresponsive to feedback signals ADJ_GAIN_1 and ADJ_GAIN_2 from theDynamic Gain Adjust process 1800.

[0096] The magnitude of Motor_Vel_Der_144 is utilized to enable/disablethis function. For values less than or equal to a selected upper bounddenoted k_BLEND_UPPER_BOUND (see Velocity Blend Process below), theOffset Compensation process 1200 is enabled. For values greater than theselected upper bound, k_BLEND_UPPER_BOUND, the Offset Compensationprocess 1200 is disabled. In addition, if the HallTachVoltX1 and inputsignal is found to be outside of expected operational limits or if theTACH_FAULT diagnostic is true, Offset Compensation process 1200 may, butneed not be disabled. It is also noteworthy to appreciate that theOffset Compensation process 1200 may be configured to ensure that theoffset filters 206 hold their value when disabled.

[0097] One skilled in the art will appreciate that there can be numerouscombinations, configurations, and topologies of filters that can beemployed to perform the various outlined functionality. An exemplaryembodiment employs an integrating loop low pass filter, scaling,scheduling and summations.

[0098] The Apply Gain process 1210 is configured to receive the gainadjustments ADJ_GAIN_1 and ADJ_GAIN_2 and therefrom generate correctedvelocity outputs X1_Corr and X2_Corr. The ADJ_GAIN_1 term, from theDynamic Gain Adjust process, is applied to the uncorrected velocityoutput X1 of adaptive filter 204 to compensate for temperature and buildtolerances yielding a resultant corrected velocity is denoted X1_CORR.Likewise, the ADJ_GAIN_2 term, from the Dynamic Gain Adjust process, isapplied to the uncorrected velocity output X2 of adaptive filter 204 tocompensate for temperature and build tolerances yielding a resultantcorrected velocity denoted X2_CORR.

[0099]FIG. 28 depicts the internal process of a Phase and Magnitudeprocess 1400 where processing of algorithms is performed to ascertainmagnitude and phase relationships of the two corrected velocitiesX1_Corr, and X2_Corr. Additionally, based on a calibration threshold, itis determined which of X1_Corr, and X2_Corr is contributing the most tothe combined magnitude.

[0100] Once again, the functionality of the processes utilized in Phaseand Magnitude process 1400 is similar or at least analogous to thatdisclosed in the Get Phase process 400 as disclosed herein above.Therefore, again, reference should be made thereto for additionalunderstanding of the embodiments disclosed herein.

[0101] Inputs processed by the Phase and Magnitude process 1400 includethe uncorrected velocities X1, and X2, the corrected velocities X1_Corr,X2_Corr, a motor position denoted Motor_Position_SPI, and a calibrationadjustment signal k_Tach_Align. The motor position signalMotor_Position_SPI as detected by sensor 36 and indexed to the absoluteposition as described earlier. The calibration adjustment k_Tach_Alignallows for an initial fabrication based adjustment to addressdifferences or variations in the orientation of the sense coils 40(FIGS. 1 and 3) and the low-resolution Hall sensor set 34 (FIG. 1). Theprocess generates two primary outputs, the selected tachometer magnitudetach_vel_mag and the selected tachometer phase tach_vel_sign.

[0102] The Phase and Magnitude process 1400 independently determineswhich tachometer signal magnitude and phase to select by making acomparison with the high-resolution position Motor_Position_SPI. Themagnitude of the two corrected velocities X1_Corr and X2_Corr isdetermined at magnitude process 1402. In an exemplary embodiment,magnitude process 1402 is a square root of the sum of the squaresalgorithm 1402 is employed to determine the magnitude of the correctedvelocities X1_Corr and X2_Corr. Moreover, rounding operations and otherarithmetic numerical methods may be applied. The resultant yields avalue for TACH_VEL_MAG, which exhibits about zero dead band and issymmetrical about zero.

[0103] At comparator 1404, a determination is made to ascertain whetherone or both of the two corrected velocities X1_Corr and X2_Corr iscontributing significantly to the resultant magnitude. In response, twodiscretes, Phase_A_En, and Phase_B_En, are generated, that when set, areindicative of whether either velocity has a magnitude, which exceeds aselected threshold. In an exemplary embodiment, absolute values of thecorrected velocities X1_Corr and X2_Corr are compared with the selectedthreshold established by scheduling the tachometer magnitudetach_vel_mag with a calibration value denoted k_PHASE_SEL_THRESH. Thethreshold comparison assures that a gain correction is determined andapplied to the appropriate velocity signal in the Auto Gain Calculationprocess 1700 and Apply Gain process 1210 of the Offset Compensation1200. Here, the processing is once again analogous to that for thetrapezoidal signals in the Get Phase process 400 disclosed in theembodiments above. In an exemplary embodiment, employing sinusoidalsignals, any combination of the uncorrected velocity signals X1 and X2is possible for correction if they exceed a selected threshold.Conversely, with the trapezoidal signals of the abovementionedembodiments, one velocity signal is selected because by the nature ofthe two trapezoidal signals, one trapezoidal signal is expected to belarger than the other is. In an exemplary embodiment, the calibrationvalue k_PHASE_SEL_THRESH is selected so that the sinusoidal signalcontributing the most to the tachometer magnitude is corrected.

[0104] A second and separate comparison is performed at the DetermineSign process at 1406 to ascertain the sign associated with the magnitudecomputed above. The Determine Sign process 1406 receives as inputs theuncorrected velocities X1 and X2; the high-resolution positionMotor_Position_SPI, and the calibration adjustment signal k_Tach_Align.In and exemplary embodiment, the Determine Sign process 1406 includes,but is not limited to, a Sign Check process 1408, a Motor Position Checkprocess 1410 and a Get Sign process 1412. The Sign Check process 1408executes an evaluation of the uncorrected velocities X1 and X2 toascertain the phase or sign of each signal. The Motor Position Checkprocess 1410 compensates the high-resolution position Motor_Position_SPIwith the calibration adjustment signal, k_Tach_Align to align it withthe uncorrected velocity X1 zero crossing. Finally, the Get Sign process1412 utilizes the compensated position to extract the respective signassociated with the uncorrected velocities X1 and X2.

[0105] It should be noted that in an exemplary embodiment, thehigh-resolution position Motor_Position_SPI is implemented as a counter,and therefore, considerations and precautions to address rollover andother computational conditions and limitations are important but notnecessarily must be accounted for when performing this addition. It isalso noteworthy to appreciate that for an exemplary embodiment, at thepoint where the uncorrected velocity X1 transitions from negative topositive values, the summation of Mtr_Rel_Pos and k_TACH_ALIGN equalszero. It is also noteworthy to appreciate that for two sinusoids inquadrature, one of the sinusoids may be utilized to define the sign for180 degree increments. However, to avoid the uncertainty at or near thezero crossings it is beneficial to define and allocate a selected spanfor each of the two sinusoids to define the sign. Therefore, for 90electrical degree intervals, the sign may readily be established fromthe sign of one of the two quadrature sinusoids over a given interval.Thus, this consideration facilitates an implementation yielding amapping of motor relative position to Tach_Vel_Sign, for a 6-pole motor,is as follows in Table 1. Once again, it will be appreciated that thereare 192 counts for a span of 360 degrees. For example, consider twosinusoids, sin(θ) and cos(θ) at approximately θ=45 degrees toapproximately θ=135, sin(θ) provides a good indication sign and avoidsproximity to zero crossings. Similarly, at approximately θ=135 degreesto approximately θ=225, cos(θ) provides a good indication sign andavoids proximity to zero crossings. Likewise, at approximately θ=225degrees to approximately θ=315, −sin(θ) provides a good indication signand avoids proximity to zero crossings. Finally, at approximately θ=315degrees to approximately θ=45, −cos(θ) provides a good indication signand avoids proximity to zero crossings. TABLE 1 Mapping For EstablishingA Sign Of The Velocity Motor_Position_SPI + k_TACH_ALIGN (Counts)Tach_Vel_Sign  0 to 23   X2 24 to 71   X1  72 to 119 −X2 120 to 167 −X1168 to 191   X2

[0106] Again, it will be understood that those skilled in the art mayconceive of variations and modifications to the preferred embodimentshown above. For example, one skilled in the art would recognize thatthe phase information could have also been acquired by variousmathematical methods applicable to sinusoids, including, but not limitedto inverse tangent, CORDIC algorithms, or merely by utilizing theposition information alone. In an exemplary embodiment, the signdetermination may be resultant from comparison of the uncorrectedvelocities X1 and X2 with the high-resolution positionMotor_Position_SPI. Contrary to the processing employed for trapezoidalsignals in the embodiments disclosed above, the sign determinationherein is potentially less sensitive to the precise positioning andtiming on the sinusoidal waveforms. Moreover, it is also noteworthy toappreciate that an alignment of the position and velocity signals asdisclosed, is not necessary for the disclosed embodiments. It merelyprovides a simplification in the understanding, terminology, andprocessing associated with the velocity and position signals in thecontext of a control system for an electric machine.

[0107] Turning now to the Apply Gain Function 1500 (FIG. 26), theselected tachometer magnitude, tach_vel_mag is scaled to the appropriatemagnitude and thereafter combined with the tachometer phasetach_vel_sign to reformulate a vector quantity velocity denotedTACH_VELOCITY_HR. The magnitude gain termed, MAG_GAIN, from the DynamicGain Adjust process 1800, is applied to schedule the tachometermagnitude TACH_VEL_MAG to compensate for temperature and buildvariations. Inputs to the Apply Gain Function 1500 include thetachometer magnitude, tach_vel_mag, the tachometer phase, tach_vel_sign,and a MAG_GAIN term, from the Dynamic Gain Adjust process 1800. Outputfrom the Apply Magnitude Gain Function 1500 is a vector quantityvelocity denoted TACH_VELOCITY_HR. It is noteworthy to appreciate thatin an exemplary embodiment, to facilitate implementation of the velocitydetermination processes, the gain scheduling, including the magnitudefeedback, is partitioned into pre and post scheduling. Such an approachaids in addressing numerical methods implementation considerations suchas overflow, word size and resolution. It should also be appreciatedthat the disclosed embodiment enumerates a method of performing thefunction but should not be taken as a limitation. Various alternativeswill be apparent for implementation of the adaptive nature of theblended velocity determination and more specifically the magnitudefeedback as computed by the Auto Gain Calculation 1700 and Dynamic GainAdjust 1800 as applied to the Offset Compensation 1200.

[0108] Turning now to the Velocity Blend process 1600 depicted in FIG.29, predetermined algorithms determine a blended velocity output. TheVelocity Blend process 1600 utilizes the vector quantity velocitydenoted TACH_VELOCITY_HR, the derived velocity Motor_Vel_Der_144, itsabsolute value, and a tachometer fault signal denoted TACH_FAULT togenerate the blended velocity Blend_Velocity_HR. In an exemplaryembodiment, a blended velocity solution is utilized to avoid thepotential undesirable effects of transients resultant from rapidtransitions between the derived velocity Motor_Vel_Der 144 and thetachometer-measured and determined velocity TACH_VELOCITY_HR. In anexemplary embodiment, the Velocity Blend process 1600, at Blend Ratio1604, selects based upon the magnitude of the absolute value of derivedvelocity Motor_Vel_Der_144 determined at block 1602, a level ofscheduling/blend ratio to be utilized. The resultant of the Blend Ratio1604 process defining a percentage or ratio to be applied atscheduler(s) 1606 and 1608 of the derived velocity Motor_Vel_Der_144 andthe compensated, measured, and scheduled velocity TACH_VELOCITY_HRrespectively. Summer 1610 adds the scheduled velocities to generate theblended composite velocity signal. The blended composite velocity signalcomprises a combination of the tachometer measured velocity and thederived velocity yet without the negative effects of saturation orexcessive time delays.

[0109] In an exemplary embodiment, the Velocity Blend Process 1600employs two calibratable breakpoints, k_BLEND_LOWER_BOUND andk_BLEND_UPPER_BOUND to select the appropriate blend. The Velocity BlendProcess 1600 linearly ramps between about 0% at the lower boundcharacterized by, for example, tachometer-based velocity only, to about100% at the upper bound characterized by position-based derived velocityonly. Once again, in an exemplary embodiment, the absolute value of thederived velocity Motor_Vel_Der_144 is used as the index into the rampfunction between the two velocities.

[0110] When both calibration points are equal to zero, the VelocityBlend Process 1600 outputs the derived motor velocity signalMotor_Vel_Der_144, only. It will be understood that disclosed herein isan exemplary embodiment illustrative as to how the blending may beperformed. It will be appreciated that many other methodologies areconceivable within the scope of the disclosure herein and of the claims.

[0111] The blending of velocities as disclosed for the Velocity BlendProcess 1600, may also be limited to selected operational constraints,for example, to enhance performance, address inherent signalcharacteristics, or to address signal validity. Therefore, in anexemplary embodiment, a diagnostic signal TACH_FAULT applied to theBlend Ratio 1604 process is utilized to disable blends based upon thetachometer-based, measured velocity TACH_VELOCITY_HR constraining theoutput to that of derived velocity Motor_Vel_Der_144 only. For example,the tachometer-based velocity blend and output may be disabled duringcertain controller processes, which would result in inaccurateinformation. For example, motor position initialization, and motorposition calibration walk functions.

[0112]FIG. 30 depicts the Auto Gain Calculation process 1700, whichincludes, but is not limited to, processes to compare the tachometervelocity, Tach_Vel_HR with the derived velocity, Motor_Vel_Der_144 togenerate a gain correction that is ultimately utilized to schedule theuncorrected velocities X1 and X2 in the Apply Gain Process 1300. In anexemplary embodiment to facilitate a particular implementation, inputsto the Auto Gain Calculation process 1700 include the derived velocityMotor_Vel_Der_144, the TACH_VELOCITY_HR signal, the Phase_A_En andPhase_B_En from the Phase and Magnitude process 1400 to generate asoutputs two gain correction factors GAIN_1 and GAIN_2. The gaincorrection factors GAIN_1 and GAIN_2 are transmitted to the Dynamic GainAdjust process 1800 for scaling and scheduling.

[0113] In an exemplary embodiment, the Auto Gain Calculation process1700 includes, but is not limited to, an Align to Polled process 1710and a Gain Process 1750. The Align to Polled process 1710, once again,is analogous to processes disclosed earlier, namely the Align to Polledprocess 800. Reference should also be made to that disclosure foradditional information. The Align to Polled process 1710 is configuredto time shift the tachometer velocity Tach_Vel_HR to facilitate a timecoherent comparison with the derived velocity Motor_Vel_Der_144. Thetime shift may include, but not be limited to a filteringimplementation. In an exemplary embodiment, a four state moving averagefilter is utilized. Moreover, it will be appreciated that the filteringfor selected signals may be limited to selected operational ranges orthe address the validity, characteristics of the signal being filtered.For example, in the disclosed embodiment, the tachometer magnitude,tach_vel_mag is filtered only when it is within a valid range.Otherwise, the derived velocity Motor_Vel_Der_144 is applied to thefilter to maintain the filter state value. It will be appreciated, thatsuch a scheme is one commonly employed to address numerical methodsconstraints encountered in implementing a filter, especially a digitallyimplemented filter.

[0114] Absolute value process 1712 and selection switch Velocity ValueSelect process 1714 facilitate determination of a valid range. The validrange for the tachometer magnitude tach_vel_mag is determined based uponthe magnitude (absolute value) of the derived velocityMotor_Vel_Der_144. Once, again, as stated earlier, it will beappreciated that the validity of the tachometer signals and ultimatelythe tachometer velocity Tach_Vel_HR is related to high speed saturation,while for the derived velocity Motor_Vel_Der_144 it is a function offiltering latency at very low speed. The selection switch, VelocityValue Select 1714 is responsive to the magnitude of the derived velocityMotor_Vel_Der_144 controls the application of the tachometer velocityTach_Vel_HR signal to the filter.

[0115] A filter 1716 is employed to facilitate generation of the timedelay. The appropriate time delay is determined based upon the totaltime delay that the derived velocity signals experience relative to thetachometer signals. The time shift accounts for the various signal andfiltering effects on the analog signals and the larger time delayassociated with filtering the derived velocity signal. As statedearlier, the derived velocity signal experiences a significant filteringlag, especially at lower speeds. Introducing this shift yields a resultthat makes the tachometer signals readily comparable to the derivedvelocity. The selected signal is thereafter delivered as an output asFiltered_Tach_Vel.

[0116] In a preferred embodiment, the resultant filter 1716 is a fourstate moving average filter similar to the filter 104 (FIG. 8)implemented in the Speed Estimation process 1100. One skilled in the artwill recognize that there can be numerous combinations, configurations,and topologies of filters that can satisfy provide similar functionalityand that a particular configuration selected for an implementationshould not be considered as limiting.

[0117] Continuing with FIG. 30, the Gain process 1750 executes a processwhere an error is generated and subsequently utilized to compute a gaincorrection in the adaptive feedback algorithm. The Gain process 1750effectively forms the feedback of an adaptive servo loop to control themagnitude of the tachometer velocity signal. In an implementation of anexemplary embodiment, an integrator 1760 drives the error in themagnitude of the velocity signal to substantially zero. In an exemplaryembodiment, the error is resultant from a comparison and errorgeneration at Error Determination 1752. The comparison is of theabsolute value of the derived velocity Motor_Vel_Der_144 to the absolutevalue of the filtered tachometer velocity Filtered_Tach_Vel. Theresulting error is thereafter, applied to a Select function 1756. Underpredetermined conditions, controlled by Enable Gain function 1754, whichenables or disables the error signal, the Select function 1756 passesthe error to the error integrator(s) 1760. The Enable Gain function 1754allows the error to be utilized for error gain computation only when theerror is valid. For example, the error is valid when both the filteredtachometer velocity and the derived velocity are within a valid range.In an exemplary embodiment, the error is utilized when the magnitude ofthe Motor_Vel_Der_144 signal is between 16 and 66.4 radians per second.However, the error is not utilized for error gain computation if theabsolute value of the Motor_Vel_Der_144 signal is less than or exceeds aselected limits. In a particular implementation of an exemplaryembodiment, limits of 72 radians per second or is less than 10.4 radiansper second are employed. It should be appreciated that under someconditions, the comparison of the two velocities and the generation ofan error may not be valid. For example, at very small velocities, thederived velocity, Motor_Vel_Der_144 exhibits excessive delay, while atlarger velocities, that is, in excess of 72 radians per second, thetachometer signals may be saturated, and therefore an inaccuratedepiction of the actual velocity.

[0118] Returning to FIG. 30, in an exemplary embodiment, the Selectfunction 1756 transmits the error, when enabled, to an error integrator1760, (in this instance two integrators). The integrator(s) 1760, underselected conditions, integrate(s) the error to generate a gainadjustment feedback denoted GAIN_1 and GAIN_2. The selection of whichintegrator 1760 operates on the error is controlled by time shiftedversions of the discretes Phase_A_En and Phase_B_En resultant from delay1758 that indicate which corrected velocity X1_CORR or X2_COOR, iscontributing the majority of the tachometer magnitude, tach_vel_mag. Inan exemplary embodiment, the integrator 1760 also maintains its outputconstant when not enabled. The two gain integrands GAIN_1 and GAIN_2form the gain adjustment feedback that is then utilized as an input inthe abovementioned Dynamic Gain Adjust process 1800 and ultimately atthe Offset Compensation process 1200.

[0119] Continuing with FIG. 30, it is noteworthy to appreciate that theintegration envelope boundaries may be implemented with a variety ofboundary conditions. For example, “hard” boundaries, which areexemplified by the integrator(s) 1760 being either “on,” and running, or“off” when on either side of the boundary respectively. Conversely,“soft” boundaries, where the integrator gain is gradually reduced whencrossing the boundary from the “on” or active side to the “off” orinactive side and gradually increased back to its nominal value whencrossing the boundary from the “off” side to the “on” side. A “hard”boundary may be easier to implement but a “soft” boundary may allow theintegration window to grow slightly. In an embodiment as disclosedherein, a “hard” boundary may be employed to simplify implementationrequirements.

[0120] Having reviewed the interfaces to, and operation of, theintegrators 1760, attention may now be given to some details ofoperation of the remainder of the Gain process 1750 as depicted in FIG.30. It may be noted that the parameters of interest usually varyrelatively slowly over time. For example, the temperature dependentvariation and the life variation of the parameters may exhibit timeconstants on the order of minutes, days if not even years. Therefore,the integrator(s) 1760 may be configured as desired to exhibitrelatively slow response times, or low gains. Setting the gains too highor the response too fast, for example, may inadvertently cause theintegrator(s) 1760 to initiate corrections during higher frequencyvariations in velocity as might be experienced under accelerations orrapid or aggressive inputs. Moreover, with excessively high integratorgain, the tachometer velocity may respond to high frequency noise orultimately become unstable. Therefore, by maintaining the integrator(s)1760 gains lower and the response characteristics of the integrator(s)1760 slower, overall response to erroneous velocity transients, if any,are limited and adverse effects to the outputs are minimized. Thus, inan exemplary embodiment, the integrator(s) 1760 may be disabled underselected conditions to ensure that the effect on the two gain integrandsGAIN_1 and GAIN_2 will be minimized.

[0121] Another important consideration for the practical implementationemploying integrator(s) 1760 is initialization. It is well understoodthat because of the nature of an integrating function, controlling theinitial conditions is very important. This is the case because any errorin the initial conditions may only be eliminated via the gain and at theintegrating rate specified. Therefore, for example, where the desiredresponse is purposefully maintained slow to accommodate systemcharacteristics, the initial error may require a significant duration oftime to be completely eradicated.

[0122] To address the abovementioned initialization concerns it isappreciated that the integrator(s) 1760 may be reset to a zero valuewith each application of power. It is also noteworthy to appreciate thatsuch an initialization may introduce an error into the gain adjustmentfeedback denoted GAIN_1 and GAIN_2, which could require a relativelylong time to be significantly reduced or eliminated. As a result, aninaccurate gain feedback may be provided and thereby an erroneousvelocity output provided. Such an error may be acceptable in someapplications and yet be objectionable in others and therefore moresophisticated initialization schemes may prove beneficial.

[0123] In an alternative embodiment, another approach is consideredwhere the integrator(s) 1760 is initialized to a nominal parameter value(as opposed to reset to zero) with each initialization or startingcondition (e.g., with each power on cycle or ignition cycle in anautomobile). However, employing this approach once again means that atinitial power turn on (key on) the a gain adjustment feedback denotedGAIN_1 and GAIN_2 applied to the Dynamic Gain Adjust process 1800 andultimately at the Offset Compensation process 1200 will now start at anominal parameter value. Moreover, an initialization to a nominalparameter value or zero will not include any information about the gainadjustment feedback “learned” during previous operational cycles. Whileboth the abovementioned approaches address the possibility for erroraccumulation in the integrator, introduction of an error on eachinitialization may yield less than satisfactory results. Consideringthat the output of the integrator(s) 1760 is effectively the errors“learned” over a period of operation, this means that for the firstutilization of the tachometer velocity, a significant, error may bepresent. For example, with steering applications an incorrect velocitygain would result in inaccurate velocity damping, yielding undesirablesteering system response.

[0124] In yet another embodiment, the output of the integrator 1760 maybe saved in a storage location at the end of each ignition/operationalcycle. It is noteworthy to recognize that at the end of each ignitioncycle, the output of the integrator(s) 1760 represents the gainadjustment needed to overcome the build, life, and temperature errorsand variations. Furthermore, it should be noted and apparent that fromone operational cycle to the next, the gain adjustment dependent uponbuild variations will not have changed significantly and therefore, thebuild variation error correction required is zero. Likewise, the lifevariation correction from one operational cycle (e.g., each powerapplication) to the next is minimal if not negligible. Only thevariation due to temperature changes is likely to be significant.Therefore, in an embodiment, the output of the integrator(s) 1760 may becompared with values from previous operational cycles and saved as ainitialization correction only if they differ from the saved values bysome selected margin. If variations due to temperature changes aredetermined to be significant, they may be compensated by normalizing thestored values to a given reference temperature and then adjusting forthe actual temperature when the stored values are retrieved. In thismanner, the stored values will only change from one operational cycle tothe next as a result of life variation or temperature measurementerrors. As such, only significant differences in the response of theintegrator(s) 1760 between operational cycles will be saved, therebyreducing processing effort and impact on storage utilization. An exampleof normalizing the stored values for temperature is to store the valueGo in the following formula:

Go=G/(1+a(T−To))

[0125] where,

[0126] G is the current gain for the error integrator(s)

[0127] Go is the normalized gain to be stored

[0128] a is the thermal coefficient of the tachometer gain

[0129] T is the current temperature of the tachometer

[0130] To is the reference temperature (typically 25 degrees Celsius).

[0131] Likewise, upon the beginning of the next operational cycle, thetemperature variation can be compensated by inverting the above formulaas follows:

G=Go(1+a(T−To)).

[0132] It should once again be appreciated that disclosed herein is anexemplary embodiment for practicing the invention which should beconsidered without limitation. A particular configuration andimplementation has been described to facilitate understanding. Forexample, it should be understood that the disclosed methods andfunctions for the disclosed processes such as Select function 1756 anderror integrators 1760 merely operate as implementations of a particularexemplary embodiment. Numerous variations and implementations should beapparent to those skilled in the art. For example, error accumulationmay be accomplished via summers, counters, integrators and the like, aswell as combinations including at least one of the foregoing withoutlimitation thereof.

[0133] Returning now to FIG. 25 and the Dynamic Gain Adjust process1800, which includes, but is not limited to, processes to formulate thetwo gain adjustment outputs ADJ_GAIN_1; ADJ_GAIN_2; and a magnitude gaincommand MAG_GAIN which are resultant of scheduling of the two gaincorrection factors GAIN_1 and GAIN_2. The two gain adjustmentsADJ_GAIN_1; ADJ_GAIN_2 form the gain adjustment feedback that isutilized as an input in the abovementioned Offset Compensation 200. Inan exemplary embodiment, the Dynamic Gain Adjust 1800 process computesthe above-mentioned corrections as combinations, scaling and schedulingof the two gain integrands GAIN_1 and GAIN_2. For example, in a simpleform, the MAG_GAIN is computed as the sum of the two gain integrandsGAIN_1 and GAIN_2. In addition, the gain adjustment ADJ_GAIN_1 iscomputed as the gain integrand GAIN_1, scaled, and then divided by thesum MAG_GAIN. Likewise, the gain adjustment ADJ_GAIN_2 is computed asthe gain integrand GAIN_2, scaled, and then divided by the sum MAG_GAIN.

[0134] The system and methodology described in the numerous embodimentshereinbefore provides a robust design and methods to determine avelocity of an electric machine. In addition, the disclosed inventionmay be embodied in the form of computer-implemented processes andapparatuses for practicing those processes. The present invention canalso be embodied in the form of computer program code containinginstructions embodied in tangible media, such as floppy diskettes,CD-ROMs, hard drives, or any other computer-readable storage medium,wherein, when the computer program code is loaded into and executed by acomputer, the computer becomes an apparatus for practicing theinvention. The present invention can also be embodied in the form ofcomputer program code, for example, whether stored in a storage medium,loaded into and/or executed by a computer, or as data signal transmittedwhether a modulated carrier wave or not, over some transmission medium,such as over electrical wiring or cabling, through fiber optics, or viaelectromagnetic radiation, wherein, when the computer program code isloaded into and executed by a computer, the computer becomes anapparatus for practicing the invention. When implemented on ageneral-purpose microprocessor, the computer program code segmentsconfigure the microprocessor to create specific logic circuits.

[0135] While the invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. An apparatus for determining the velocity of a rotating devicecomprising: a rotational part having a magnet assembly affixed to arotating shaft of said rotating device configured to rotate about arotation axis; and a circuit assembly including, a circuitinterconnection having a sense coil, a sensor affixed to said circuitassembly, said circuit assembly adapted to be in proximity to saidmagnet assembly; wherein said magnet assembly combines with said circuitassembly to form an air core electric machine such that voltagegenerated from said sense coil exhibits an amplitude proportional tosaid velocity.
 2. The apparatus of claim 1 wherein said magnet assemblyis arranged in an annular ring, concentric with said rotation axis ofsaid rotational part.
 3. The apparatus of claim 2 wherein said magnetassembly comprises alternating poles equivalently sized and distributedabout said annular ring at a circumference thereof.
 4. The apparatus ofclaim 2 wherein said magnet assembly is oriented such that a magneticfield therefrom radiates in an axial direction, parallel to saidrotation axis.
 5. The apparatus of claim 2 wherein said annular ring isarranged such that a surface radiating said magnetic field is placedproximal to said circuit assembly orthogonal to said rotation axis ofsaid rotational part.
 6. The apparatus of claim 2 wherein said magnetassembly includes a low-resolution magnet set.
 7. The apparatus of claim2 wherein said low-resolution magnet set includes six poles.
 8. Theapparatus of claim 7 wherein said magnet assembly includes ahigh-resolution magnet set.
 9. The apparatus of claim 7 wherein saidhigh-resolution magnet set includes seventy two poles.
 10. The apparatusof claim 8 wherein said low-resolution magnet set form an annulus ofsmaller radius than a second annulus formed from said high-resolutionmagnet set.
 11. The apparatus of claim 1 wherein said sensor is a Halleffect sensor.
 12. The apparatus of claim 1 wherein said circuitinterconnection is a printed circuit card.
 13. The apparatus of claim 1wherein said circuit interconnection is a flexible circuit.
 14. Theapparatus of claim 1 wherein said circuit interconnection is on aceramic substrate.
 15. The apparatus of claim 1 wherein said circuitinterconnection is a lead frame assembly.
 16. The apparatus of claim 1further including another sense coil to form a plurality of sense coilsand wherein voltages generated from each said sense coil of saidplurality of sense coils exhibits an amplitude proportional to saidvelocity.
 17. The apparatus of claim 16 wherein said circuitinterconnection includes circuit elements including each sense coil ofsaid plurality of sense coils formed therein.
 18. The apparatus of claim16 wherein said each sense coil of said plurality of sense coilscomprises a conductive winding arranged in a spiraling serpentinefashion on one or more layers of said circuit interconnection.
 19. Theapparatus of claim 18 wherein each of said sense coils of said pluralityof sense coils are rotated relative to one another about a center ofsaid rotation axis of said rotational part to cause voltages induced oneach said sense coil of said plurality of sense coils to be inquadrature.
 20. The apparatus of claim 19 wherein each of said sensecoils of said plurality of sense coils are configured to cause voltagesinduced on said each sense coil of said plurality of sense coils to besubstantially sinusoidal.
 21. The apparatus of claim 19 wherein each ofsaid sense coils of said plurality of sense coils are configured tocause voltages induced on said each sense coil of said plurality ofsense coils to be substantially trapezoidal.
 22. The apparatus of claim18 wherein said each said sense coil of said plurality of sense coilsspiral concentrically, about said rotation axis of said rotational part,inward toward said center on a first layer and outward from said centeron a second layer.
 23. The apparatus of claim 16 wherein each said sensecoils of said plurality of sense coils includes a winding includingactive segments characterized by radial portions of said winding andinactive segments, characterized by circumferential portions of said atleast one winding.
 24. The apparatus of claim 23 wherein said activesegments intersect lines of magnetic flux from said low-resolutionmagnet set of said magnet assembly to induce a voltage on each saidsense coil of said plurality of sense coils.
 25. The apparatus of claim23 wherein a velocity vector of said lines of magnetic flux from saidlow-resolution magnet set of said magnet assembly intersect said activesegments at approximately ninety degrees.
 26. The apparatus of claim 23wherein said inactive segments intersect said lines of magnetic fluxfrom a low-resolution magnet set of said magnet assembly while limitinginducement of a voltage on each said sense coil of said plurality ofsense coils.
 27. The apparatus of claim 26 wherein a velocity vector ofsaid lines of magnetic flux from said low-resolution magnet set of saidmagnet assembly intersect said inactive segments at approximately zerodegrees.
 28. The apparatus of claim 26 wherein said inactive segments donot intersect said lines of magnetic flux from said low-resolutionmagnet set of said magnet assembly.
 29. The apparatus of claim 23wherein said winding is arranged with an about constant average distancefrom said magnet assembly.
 30. The apparatus of claim 23 wherein saidwinding is arranged with another winding on each of two layers,concentric with said rotation axis, with 144 total active segments. 31.The apparatus of claim 23 wherein each of said sense coils of saidplurality of sense coils are configured to cause voltages induced onsaid each sense coil of said plurality of sense coils to besubstantially sinusoidal.
 32. The apparatus of claim 23 wherein each ofsaid sense coils of said plurality of sense coils are configured tosubstantially cancel selected harmonics of voltages induced on said eachsense coil of said plurality of sense coils.
 33. The apparatus of claim32 wherein each of said sense coils of said plurality of sense coils areconfigured to substantially cancel a third harmonic and fifth harmonicof voltages induced on said each sense coil of said plurality of sensecoils.
 34. The apparatus of claim 32 wherein said winding is rotatedrelative to another at least one winding about a center of said rotationaxis of said rotational part to substantially cancel a selected harmonicof voltages induced on said each sense coil of said plurality of sensecoils.
 35. The apparatus of claim 34 wherein said winding is rotatedrelative to another winding about a center of said rotation axis of saidrotational part to substantially cancel and a seventh harmonic ofvoltages induced on said each sense coil of said plurality of sensecoils.
 36. The apparatus of claim 34 wherein said selected reference isa pole center.
 37. The apparatus of claim 34 wherein a first activesegment of pairs of active segments for successive turns of said windingis rotated from a first selected reference by −18, −14, −6, −2, +2, +6,+14, and +18 degrees respectively, while a second active segment of saidpair of active segments selected reference by +18, +14, +6, +2, −2, −6,−14, and −18 degrees respectively, wherein each turn includes threepairs of active segments.
 38. The apparatus of claim 34 wherein saidwinding includes 48 active segments and said another winding includes 48active segments.
 39. The apparatus of claim 23 wherein said winding isrotated relative to said another winding about a center of said rotationaxis of said rotational part to substantially cancel a selected harmonicof voltages induced on said each sense coil of said plurality of sensecoils.
 40. The apparatus of claim 39 wherein said winding is rotatedrelative to said another winding about a center of said rotation axis ofsaid rotational part to substantially cancel and a seventh harmonic ofvoltages induced on said each sense coil of said plurality of sensecoils.
 41. The apparatus of claim 23 wherein each of said sense coils ofsaid plurality of sense coils are configured to cause voltages inducedthereon from external fields to substantially cancel.
 42. The apparatusof claim 23 wherein said winding is rotated relative to said anotherwinding about a center of said rotation axis of said rotational part tosubstantially cancel voltages induced on said winding and said anotherwinding from fields other than those produced by said magnet assembly.43. The apparatus of claim 42 wherein said winding rotated relative tosaid another winding about a center of said rotation axis of saidrotational part by 60 degrees.
 44. The apparatus of claim 23 whereinsaid winding and said another winding combine to form one of said sensecoils of said plurality of sense coils, and said winding is woundspiraling in an opposite direction of rotation of said another windingrelative to one another about a center of said rotation axis of saidrotational part.
 45. The apparatus of claim 44 wherein said winding iswound spiraling clockwise on a first layer and said another winding iswound counter clockwise on a second layer.
 46. The apparatus of claim 44wherein said winding is wound spiraling radially in a same direction assaid another winding relative to said rotation axis of said rotationalpart.
 47. The apparatus of claim 44 wherein said winding is woundspiraling in an opposite direction radially of another winding relativeto said rotation axis of said rotational part.
 48. The apparatus ofclaim 23 wherein said active segments on said winding and said anotherwinding are rotated so that contributions therefrom to voltages inducedon said winding and said another winding are cummulatative, and whereinsaid inactive segments on said winding and said another windings arerotated so that contributions therefrom to voltages induced on saidwinding and said another winding are substantially cancelled.
 49. Theapparatus of claim 48 wherein said inactive segments on said winding andsaid another winding are oriented to substantially cancel voltagesinduced on said winding and said another winding from fields other thanthose produced by said magnet assembly.
 50. The apparatus of claim 41further including a cancellation coil wherein said cancellation coil isconfigured to cause voltages induced on said plurality of sense coilsfrom external fields to substantially cancel.
 51. The apparatus of claim50 wherein said cancellation coil comprises substantially an equalnumber turns at a substantially equivalent average diameter as saidsense coil wound in an opposite direction of a sense coil.
 52. Theapparatus of claim 51 wherein said cancellation coil is configuredsimilar to said sense coil of said plurality of sense coils includingportions similar to said inactive segments, whereby said cancellationcoil is insensitive to magnetic fields from said magnet assembly and yetresponsive to external magnetic fields.
 53. The apparatus of claim 17wherein said plurality sense coils are formed in sets of spirals notconcentric with said rotation axis of said rotational part.
 54. Theapparatus of claim 3 wherein said magnet assembly is oriented such thata magnetic field therefrom radiates in the radial direction, orthogonalto said rotation axis.
 55. The apparatus of claim 54 further includinganother sense coil to form a plurality of sense coils.
 56. The apparatusof claim 55 wherein said plurality of sense coils are arranged such thatsaid active segments are oriented in an axial direction, parallel tosaid rotation axis.
 57. The apparatus of claim 56 wherein a velocityvector of said lines of magnetic flux from a low-resolution magnet setof said magnet assembly intersect said active segments at approximatelyninety degrees.
 58. The apparatus of claim 56 wherein a velocity vectorof said lines of magnetic flux from a low-resolution magnet set of saidmagnet assembly intersect said inactive segments at approximately zerodegrees.
 59. A system for determining a velocity of a rotating devicecomprising: an apparatus having a rotational part including a magnetassembly affixed to a rotating shaft of said rotating device configuredto rotate about a rotation axis; a circuit assembly, including a circuitinterconnection having a sense coil as an integral member, a sensoraffixed to said circuit assembly, mounted in close proximity to saidmagnet assembly; wherein said magnet assembly combines with said circuitassembly to form an air core electric machine such that voltagesgenerated from each sense coil exhibits an amplitude proportional tosaid velocity; a controller operatively coupled to said circuitassembly, said controller configured to execute an adaptive algorithmincluding: receiving a position signal related to rotational positiontransmitted to said controller; determining a derived velocity signalutilizing said position signal; receiving a tachometer velocity signal;determining a compensated velocity signal in response to said tachometervelocity signal; blending said compensated velocity signal with saidderived velocity signal under selective conditions to generate a blendedvelocity output indicative of the velocity of said rotating device. 60.The system of claim 59 wherein said magnet assembly is arranged in anannular ring, concentric with said rotation axis of said rotationalpart.
 61. The system of claim 60 wherein said magnet assembly comprisesalternating poles equivalently sized and distributed about said annularring at a circumference thereof.
 62. The system of claim 60 wherein saidmagnet assembly is oriented such that a magnetic field therefromradiates in an axial direction, parallel to said rotation axis.
 63. Thesystem of claim 60 wherein said annular ring is arranged such that asurface radiating said magnetic field is placed proximal to said circuitassembly orthogonal to said rotation axis of said rotational part. 64.The system of claim 60 wherein said magnet assembly includes alow-resolution magnet set.
 65. The system of claim 60 wherein saidlow-resolution magnet set includes six poles.
 66. The system of claim 65wherein said magnet assembly includes a high-resolution magnet set. 67.The system of claim 65 wherein said high-resolution magnet set includesseventy two poles.
 68. The system of claim 66 wherein saidlow-resolution magnet set form an annulus of smaller radius than asecond annulus formed from said high-resolution magnet set.
 69. Thesystem of claim 59 wherein said sensor is a Hall effect sensor.
 70. Thesystem of claim 59 wherein said circuit interconnection is a printedcircuit card.
 71. The system of claim 59 wherein said circuitinterconnection is a flexible circuit.
 72. The system of claim 59wherein said circuit interconnection is on a ceramic substrate.
 73. Thesystem of claim 59 wherein said circuit interconnection is a lead frameassembly.
 74. The system of claim 59 further including another sensecoil to form a plurality of sense coils and wherein voltages generatedfrom each said sense coil of said plurality of sense coils exhibits anamplitude proportional to said velocity.
 75. The system of claim 74wherein said circuit interconnection includes circuit elements includingeach sense coil of said plurality of sense coils formed therein.
 76. Thesystem of claim 74 wherein said each sense coil of said plurality ofsense coils comprises a conductive winding arranged in a spiralingserpentine fashion on one or more layers of said circuit assembly. 77.The system of claim 76 wherein each of said sense coils of saidplurality of sense coils are rotated relative to one another about acenter of said rotation axis of said rotational part to cause voltagesinduced on each said sense coil of said plurality of sense coils to bein quadrature.
 78. The system of claim 77 wherein each of said sensecoils of said plurality of sense coils are configured to cause voltagesinduced on said each sense coil of said plurality of sense coils to besubstantially sinusoidal.
 79. The system of claim 77 wherein each ofsaid sense coils of said plurality of sense coils are configured tocause voltages induced on said each sense coil of said plurality ofsense coils to be substantially trapezoidal.
 80. The system of claim 76wherein said each said sense coil of said plurality of sense coilsspiral concentrically, about said rotation axis of said rotational part,inward toward said center on a first layer and outward from said centeron a second layer.
 81. The system of claim 74 wherein each said sensecoils of said plurality of sense coils includes a winding includingactive segments characterized by radial portions of said winding andinactive segments, characterized by circumferential portions of said atleast one winding.
 82. The system of claim 81 wherein said activesegments intersect lines of magnetic flux from said low-resolutionmagnet set of said magnet assembly to induce a voltage on each saidsense coil of said plurality of sense coils.
 83. The system of claim 81wherein a velocity of said lines of magnetic flux from saidlow-resolution magnet set of said magnet assembly intersect said activesegments at approximately ninety degrees.
 84. The system of claim 81wherein said inactive segments intersect said lines of magnetic fluxfrom a low-resolution magnet set of said magnet assembly while limitinginducement of a voltage on each said sense coil of said plurality ofsense coils.
 85. The system of claim 84 wherein a velocity of said linesof magnetic flux from said low-resolution magnet set of said magnetassembly intersect said inactive segments at approximately zero degrees.86. The system of claim 84 wherein said inactive segments do notintersect said lines of magnetic flux from said low-resolution magnetset of said magnet assembly.
 87. The system of claim 81 wherein saidwinding is arranged with an about constant average distance from saidmagnet assembly.
 88. The system of claim 81 wherein said winding isarranged with another winding on each of two layers, concentric withsaid rotation axis, with 144 total active segments.
 89. The system ofclaim 81 wherein each of said sense coils of said plurality of sensecoils are configured to cause voltages induced on said each sense coilof said plurality of sense coils to be substantially sinusoidal.
 90. Thesystem of claim 81 wherein each of said sense coils of said plurality ofsense coils are configured to substantially cancel selected harmonics ofvoltages induced on said each sense coil of said plurality of sensecoils.
 91. The system of claim 90 wherein each of said sense coils ofsaid plurality of sense coils are configured to substantially cancel athird harmonic and fifth harmonic of voltages induced on said each sensecoil of said plurality of sense coils.
 92. The system of claim 90wherein said winding is rotated relative to another at least one windingabout a center of said rotation axis of said rotational part tosubstantially cancel a selected harmonic of voltages induced on saideach sense coil of said plurality of sense coils.
 93. The system ofclaim 92 wherein said winding is rotated relative to another windingabout a center of said rotation axis of said rotational part tosubstantially cancel and a seventh harmonic of voltages induced on saideach sense coil of said plurality of sense coils.
 94. The system ofclaim 92 wherein said selected reference is a pole center.
 95. Thesystem of claim 92 wherein a first active segment of pairs of activesegments for successive turns of said winding is rotated from a firstselected reference by −18, −14, −6, −2, +2, +6, +14, and +18 degreesrespectively, while a second active segment of said pair of activesegments selected reference by +18, +14, +6, +2, −2, −6, −14, and −18degrees respectively, wherein each turn includes three pairs of activesegments.
 96. The system of claim 92 wherein said winding includes 48active segments and said another winding includes 48 active segments.97. The system of claim 81 wherein said winding is rotated relative tosaid another winding about a center of said rotation axis of saidrotational part to substantially cancel a selected harmonic of voltagesinduced on said each sense coil of said plurality of sense coils. 98.The system of claim 97 wherein said winding is rotated relative to saidanother winding about a center of said rotation axis of said rotationalpart to substantially cancel and a seventh harmonic of voltages inducedon said each sense coil of said plurality of sense coils.
 99. The systemof claim 81 wherein each of said sense coils of said plurality of sensecoils are configured to cause voltages induced thereon from externalfields to substantially cancel.
 100. The system of claim 81 wherein saidwinding is rotated relative to said another winding about a center ofsaid rotation axis of said rotational part to substantially cancelvoltages induced on said winding and said another winding from fieldsother than those produced by said magnet assembly.
 101. The system ofclaim 100 wherein said winding rotated relative to said another windingabout a center of said rotation axis of said rotational part by 60degrees.
 102. The system of claim 81 wherein said winding and saidanother winding combine to form one of said sense coils of saidplurality of sense coils, and said winding is wound spiraling in anopposite direction of rotation of said another winding relative to oneanother about a center of said rotation axis of said rotational part.103. The system of claim 102 wherein said winding is wound spiralingclockwise on a first layer and said another winding is wound counterclockwise on a second layer.
 104. The system of claim 102 wherein saidwinding is wound spiraling radially in a same direction as said anotherwinding relative to said rotation axis of said rotational part.
 105. Thesystem of claim 102 wherein said winding wound spiraling in an oppositedirection radially of another winding relative to said rotation axis ofsaid rotational part.
 106. The system of claim 81 wherein said activesegments on said winding and said another winding are rotated so thatcontributions therefrom to voltages induced on said winding and saidanother winding are cummulatative, and wherein said inactive segments onsaid winding and said another windings are rotated so that contributionstherefrom to voltages induced on said winding and said another windingare substantially cancelled.
 107. The system of claim 106 wherein saidinactive segments on said winding and said another winding are orientedto substantially cancel voltages induced on said winding and saidanother winding from fields other than those produced by said magnetassembly.
 108. The system of claim 99 further including a cancellationcoil wherein said cancellation coil is configured to cause voltagesinduced on said plurality of sense coils from external fields tosubstantially cancel.
 109. The system of claim 108 wherein saidcancellation coil comprises substantially an equal number turns at asubstantially equivalent average diameter as said sense coil wound in anopposite direction of a sense coil.
 110. The system of claim 109 whereinsaid cancellation coil is configured similar to said sense coil of saidplurality of sense coils including portions similar to said inactivesegments, whereby said cancellation coil is insensitive to magneticfields from said magnet assembly and yet responsive to external magneticfields.
 111. The system of claim 75 wherein said plurality sense coilsare formed in sets of spirals not concentric with said rotation axis ofsaid rotational part.
 112. The system of claim 61 wherein said magnetassembly is oriented such that a magnetic field therefrom radiates inthe radial direction, orthogonal to said rotation axis.
 113. The systemof claim 112 further including another sense coil to form a plurality ofsense coils.
 114. The system of claim 113 wherein said plurality ofsense coils are arranged such that said active segments are oriented inan axial direction, parallel to said rotation axis.
 115. The system ofclaim 114 wherein a velocity vector of said lines of magnetic flux froma low-resolution magnet set of said magnet assembly intersect saidactive segments at approximately ninety degrees.
 116. The system ofclaim 114 wherein a velocity vector of said lines of magnetic flux froma low-resolution magnet set of said magnet assembly intersect saidinactive segments at approximately zero degrees.
 117. The system ofclaim 59 wherein said compensated velocity signal is the resultant of anadaptive gain control loop 100-1000, 1100-1900 configured to controlmagnitude of said compensated velocity signal under selected conditions.118. The system of claim 59 wherein said derived velocity signal isdetermined as a difference between two measured positions of saidrotating shaft divided by a time difference between said two measuredpositions; and filtering a resultant thereof.
 119. The system of claim59 further including another sense coil to form a plurality of sensecoils and wherein said controller further receives another tachometervelocity signal to form a plurality of tachometer velocity signals. 120.The system of claim 119 wherein said plurality of tachometer velocitysignals are resultants generated by said plurality of sense coilsconfigured such that the voltages generated thereby are in quadrature.121. The system of claim 119 wherein said plurality of tachometervelocity signals are substantially sinusoidal.
 122. The system of claim119 wherein said blended velocity output is generated by combining saidderived velocity signal and said compensated velocity signal underselective conditions based upon characteristics of at least one of saidderived velocity signal said plurality of tachometer velocity signals.123. The system of claim 122 wherein said selective conditions include amagnitude of said derived velocity signal.
 124. The system of claim 119wherein generating said compensated velocity signal includes: extractingrespective offsets and biases from said plurality of tachometer velocitysignals; correcting said plurality of tachometer velocity signals toproduce a plurality of corrected velocity signals; determining amagnitude signal and phase signal responsive to said plurality ofcorrected velocity signals; combining said magnitude signal with saidphase signal to formulate said compensated velocity signal; determiningan error signal; and wherein said correcting is responsive to a gainadjustment signal.
 125. The system of claim 124 wherein said extractingis accomplished by a selectable filter.
 126. The system of claim 125wherein said selectable filter conditionally subtracts low frequencyspectral components from said plurality of tachometer velocity signals.127. The system of claim 124 wherein said correcting is applied by again adjustment, wherein said gain adjustment is responsive to aselected corrected velocity signal of said plurality of correctedvelocity signals, which contributes most to said magnitude signal, andwherein said selected corrected velocity signal exceeds an establishedthreshold.
 128. The system of claim 127 wherein said establishedthreshold is indicative of a minimum magnitude signal for which saidcorrecting is desired.
 129. The system of claim 124 wherein saiddetermining a magnitude signal comprises executing a square root of asum of squares function.
 130. The system of claim 124 wherein saiddetermining a phase signal comprises selecting a sign of one of saidtachometer velocity signals from said plurality of tachometer velocitysignals under selected conditions.
 131. The system of claim 124 whereinsaid error signal is responsive to a magnitude differential between saidderived velocity signal and a time coherent version of said compensatedvelocity signal.
 132. The system of claim 124 wherein said gainadjustment is responsive to an adaptive feedback loop including an errorintegrator which is responsive to said error signal to control magnitudeof said velocity under selected conditions.
 133. The system of claim 132wherein said error integrator is initialized to a zero condition. 134.The system of claim 132 wherein said error integrator is initialized toa nominal value.
 135. The system of claim 132 wherein said errorintegrator is initialized to a saved value of said error integrator,said saved value updated with a current output of said error integratoronly if said current output of said error integrator exhibits a changein excess of a selected threshold.
 136. A method for determining avelocity of a rotating device, comprising: employing an apparatus havinga rotational part including a magnet assembly affixed to a rotatingshaft of said rotating device configured to rotate about a rotationaxis; employing a circuit assembly, including a circuit interconnectionhaving a sense coil as an integral member, a sensor affixed to saidcircuit assembly, adapted to be in close proximity to said magnetassembly; executing an algorithm in a controller operatively coupled tosaid circuit assembly, said algorithm including: receiving a positionsignal related to rotational position; determining a derived velocitysignal utilizing said position signal; receiving a tachometer velocitysignal; determining a compensated velocity signal in response to saidtachometer velocity signal; blending said compensated velocity signalwith said derived velocity signal under selective conditions to generatea blended velocity indicative of said velocity of said rotating device.137. The method of claim 136 wherein said compensated velocity signal isthe resultant of an adaptive gain control loop 100-1000, 1100-1900configured to control magnitude of said compensated velocity signalunder selected conditions.
 138. The method of claim 136 wherein saidderived velocity signal is determined as a difference in measuredpositions of said rotating device divided by a time difference betweensaid two measured positions; and filtering a resultant thereof.
 139. Themethod of claim 136 further including said controller receiving anothertachometer velocity signal to form a plurality of tachometer velocitysignals from another sense coil to form a plurality of sense coils. 140.The method of claim 139 wherein said plurality of tachometer velocitysignals are resultants generated by said plurality of sense coilsconfigured such that voltages generated thereby are in quadrature. 141.The method of claim 139 wherein said plurality of tachometer velocitysignals are substantially sinusoidal.
 142. The method of claim 139wherein said blended velocity output is generated by combining saidderived velocity signal and said compensated velocity signal underselective conditions based upon a characteristic of at least one of saidderived velocity signal and said plurality of tachometer velocitysignals.
 143. The method of claim 142 wherein said selective conditionsinclude a magnitude of said derived velocity signal.
 144. The method ofclaim 139 wherein generating said compensated velocity signal includes:extracting respective offsets and biases from said plurality oftachometer velocity signals; correcting said plurality of tachometervelocity signals to produce a plurality of corrected velocity signals;determining a magnitude signal and phase signal responsive to saidplurality of corrected velocity signals; combining said magnitude signalwith said phase signal to formulate said compensated velocity signal;determining an error signal; and wherein said correcting is responsiveto a gain adjustment signal.
 145. The method of claim 144 wherein saidextracting is accomplished by a selectable filter.
 146. The method ofclaim 145 wherein said selectable filter conditionally subtracts lowfrequency spectral components from said plurality of tachometer velocitysignals.
 147. The method of claim 144 wherein said correcting is appliedby a gain adjustment, wherein said gain adjustment is responsive to aselected corrected velocity signal of said plurality of correctedvelocity signals, which contributes most to said magnitude signal, andwherein said selected corrected velocity signal exceeds an establishedthreshold.
 148. The method of claim 147 wherein said establishedthreshold is indicative of a minimum magnitude signal for which saidcorrecting is desired.
 149. The method of claim 144 wherein saiddetermining a magnitude signal comprises executing a square root of asum of squares function.
 150. The method of claim 144 wherein saiddetermining a phase signal comprises selecting a sign of one of saidtachometer velocity signals from said plurality of tachometer velocitysignals under selected conditions.
 151. The method of claim 144 whereinsaid error signal is responsive to a magnitude differential between saidderived velocity signal and a time coherent version of said compensatedvelocity signal.
 152. The method of claim 144 wherein said gainadjustment is responsive to an adaptive feedback loop including an errorintegrator which is responsive to said error signal as part of an tocontrol magnitude of said velocity under selected conditions.
 153. Astorage medium, said storage medium including instructions for causing acontroller to implement a method for determining a velocity of arotating device comprising: employing an apparatus having a rotationalpart including a magnet assembly affixed to a rotating shaft of saidrotating device configured to rotate about a rotation axis; employing acircuit assembly, including a circuit interconnection having a sensecoil as an integral member, a sensor affixed to said circuit assembly,adapted to be in close proximity to said magnet assembly; executing analgorithm in a controller operatively coupled to said circuit assembly,said algorithm including: receiving a position signal related torotational position determining a derived velocity signal utilizing saidposition signal; receiving a tachometer velocity signal; generating acompensated velocity signal in response to said plurality of tachometervelocity signals; blending said compensated velocity signal with saidderived velocity signal under selective conditions to generate a blendedvelocity output indicative of said velocity of said rotating device.154. The storage medium of claim 153 wherein said derived velocitysignal is determined as a difference between measured positions of saidrotating device divided by a time difference between said measuredposition; and filtering a resultant thereof.
 155. The storage medium ofclaim 153 further including said controller receiving another tachometervelocity signal to form a plurality of tachometer velocity signals fromanother sense coil to form a plurality of sense coils.
 156. The storagemedium of claim 155 wherein said plurality of tachometer velocitysignals are resultants generated by said plurality of sense coilsconfigured such that voltages generated thereby are in quadrature. 157.The storage medium of claim 155 wherein said blended velocity output isgenerated by combining said derived velocity signal and said compensatedvelocity signal under selective conditions based upon a characteristicof at least one of said derived velocity signal and said plurality oftachometer velocity signals.
 158. The storage medium of claim 155wherein generating said compensated velocity signal includes: extractingrespective offsets and biases from said plurality of tachometer velocitysignals; correcting said plurality of tachometer velocity signals toproduce a plurality of corrected velocity signals; determining amagnitude signal and phase signal responsive to said plurality ofcorrected velocity signals; combining said magnitude signal with saidphase signal to formulate said compensated velocity signal; determiningan error signal; and wherein said correcting is responsive to a gainadjustment signal.
 159. A computer data signal, said data signalcomprising code configured to cause a controller to implement a methodfor determining a velocity of a rotating device comprising: employing anapparatus having a rotational part including a magnet assembly affixedto a rotating shaft of said rotating device configured to rotate about arotation axis; employing a circuit assembly, including a circuitinterconnection having a sense coil as an integral member, a sensoraffixed to said circuit assembly, adapted to be in close proximity tosaid magnet assembly; executing an algorithm in a controller operativelycoupled to said circuit assembly, said algorithm including: receiving aposition signal related to rotational position, and determining aderived velocity signal utilizing said position signal; receiving atachometer velocity signal; generating a compensated velocity signal inresponse to said tachometer velocity signal; blending said compensatedvelocity signals with said derived velocity signal under selectiveconditions to generate a blended velocity output indicative of saidvelocity of said rotating device.
 160. The computer data signal of claim159 wherein said derived velocity signal is determined as a differencebetween measured positions of said rotating device divided by a timedifference between said measured positions; and filtering a resultantthereof.
 161. The computer data signal of claim 159 further includingsaid controller receiving another tachometer velocity signal to form aplurality of tachometer velocity signals from another sense coil to forma plurality of sense coils.
 162. The computer data signal of claim 161wherein said plurality of tachometer velocity signals are resultantsgenerated by said plurality of sense coils configured such that voltagesgenerated thereby are in quadrature.
 163. The computer data signal ofclaim 161 wherein said blended velocity output is generated by combiningsaid derived velocity signal and said compensated velocity signal underselective conditions based upon a characteristic of at least one of saidderived velocity signal and said plurality of tachometer velocitysignals.
 164. The computer data signal of claim 161 wherein generatingsaid compensated velocity signal includes: extracting respective offsetsand biases from said plurality of tachometer velocity signals;correcting said plurality of tachometer velocity signals to produce aplurality of corrected velocity signals; determining a magnitude signaland phase signal responsive to said plurality of corrected velocitysignals; combining said magnitude signal with said phase signal toformulate said compensated velocity signal; determining an error signal;and wherein said correcting is responsive to a gain adjustment signal.